Lots of us will have made a New Year's resolution to either lose weight or increase fitness levels for 2015. Unfortunately, more than 90% of us are likely to have given up 2 months in. If this sounds like you, then maybe you need a bit of encouragement; a sleep and activity tracker could do just that.

Wearable health and fitness devices are all the rage right now. A recent report from Juniper Research claims that sales of the devices will triple by 2018, meaning almost 60 million of us will own one. But why are they in demand?

In essence, it is because the gadgets can literally track your every move: how many steps you have taken, how long you have been sedentary, how many calories you have burned, how many hours sleep you have had, even how many times you awoke in the night.

Not only is this information fun to pore over, it can help you take control of your health and fitness. The majority of sleep and activity trackers will allow you to set personal goals, which can encourage you to take those few extra steps a day or get an early night to ensure you get enough sleep.

So if you think a sleep and fitness tracker may get your New Year's fitness resolution back on track, read on. Medical News Today have tried and tested some of the most popular devices currently available on the market.

Jawbone UP24: detailed tracking

Jawbone are one of the leading providers of consumer technology and wearable devices, selling their products in more than 40 countries around the globe.

The Jawbone UP24 is the second sleep and fitness tracker from the company. Compatible with both Android and iOS operating systems, the Jawbone UP24 is at the top end of the sleep and activity tracker market, currently priced at around $129.99. So what do you get for your money?

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The Jawbone UP24 is made of a hypoallergenic rubber, so it is unlikely to cause any skin irritation with continuous wear.
Image credit: Jawbone

Aesthetically, the device looks stylish on the wrist. Though unadjustable, the band comes in three sizes - small, medium and large - and is available in five colors.

Compared with some other trackers, it is thin and discreet, which is a plus if you want to wear it all day and night. In addition, the band is made of a hypoallergenic rubber, so it is unlikely to cause any skin irritation with continuous wear.

At one end of the band is a USB charging connector, covered by a removable silver cap. The device takes around 80 minutes to fully charge, and the battery life lasts up to 14 days.

A syncing button sits at the other end of the band, which connects the device to the UP app via Bluetooth. The syncing button can also be used to switch the band from active to sleep mode - just remember to press it each morning and evening!

Though the band does not have a screen display, it has two LED lights that indicate what mode the band is in - sleep or active - and the charge status.

If you are looking for a tracker that gathers more detailed sleep and activity data, then the Jawbone UP24 is a good choice. As well as recording how many steps and miles you have moved, it shows how long you have been active throughout the day, the longest you have been active, how long you have been sedentary, your total calorie burn and how many of those calories were burned while active and resting.

You can set up your own personal goals through the app. If you set a goal to walk 15,000 steps a day, for example, you will receive activity tips and recommendations, which can really help you keep on track. In addition, you can connect with friends and family who have one of the devices and compete against each other, which makes exercise a bit more fun and can encourage you to up your game.

When it comes to sleep data, the device tracks your total hours spent asleep, how much time was spent in light and sound sleep, how long it took to fall asleep, how many times you woke up and how long you were awake for.

There is also a smart alarm, which is meant to wake you up at the optimal moment in your sleep cycle with a light vibration. We would recommend against using this in replacement of your alarm clock, however; your boss will not be happy.

A useful feature of the Jawbone UP24 is the idle alert - a light vibration to indicate when you have been sedentary for too long. When you are sitting at a desk for most of the day, a little nudge every couple of hours or so can really encourage you to stretch your legs, something we welcomed here at MNT.

Overall, the Jawbone UP24 is a good sleep and activity tracker for both the fitness buffs and those of us who are looking to increase our activity levels.

iHealth Edge: activity progress at the flick of a wrist

Last year, we reviewed some blood pressure monitors from self-monitoring technology company iHealth, and pointed out that only owners of Apple products could use the devices, which are compatible only with iOS - Apple's native operating system.

We found that the company's new sleep and fitness tracker iHealth Edge can be used with both the iOS and Android operating systems, however.

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With a flick of the wrist, the iHealth Edge displays the time, charge status and activity progress.
Image credit: iHealth

The first thing we noticed about this device is how bulky it is. With its large screen display, it resembles a man's watch - not so much a problem if you are a man, but women may find this device less attractive.

That said, it is comfortable on the wrist and the strap is easily adjustable. It also comes with four different colored straps - pink, orange, black and grey - so you can chop and change to match your outfit. In addition, the device comes with a waist clip, so you are not limited to wearing it on your wrist. There is also a separate sleep wristband - a feature we at MNT liked, as so many trackers are uncomfortable to wear in bed.

The device comes with a USB charging dock and can be fully charged in around 2 hours. The battery life lasts around 5 to 7 days.

Priced at around $69.99, the iHealth Edge is more of a middle-of-the-range device, and this is reflected in the data it collects: how many steps you have moved, the distance traveled, how much time you have spent working out, calories burned, how many hours you have slept and how many times you woke up. If you just want basic data, however, this tracker does the job.

You will need to download the iHealth app from the Apple or Google Play store, and data can be uploaded from the device via Bluetooth. For those of you with Apple devices, you will be pleased to know that your data can also be shared via Apple HealthKit. You are also able to set personalized activity, sleep and weight goals.

The screen display with the iHealth Edge is useful. With a flick of the wrist, it displays the time and charge status. When you walk, you are shown a dancing frog (a nice touch? You decide), followed by footprints that show you how many steps you have taken so far, so you do not have to keep looking at the app to view your data.

Another benefit to this tracker is that you do not have to switch activity modes - it automatically registers your physical and sleep activity, which is perfect if you want a "wear it and forget about it" device.

Nuband Activ+: for wearable technology newbies

For those of you who want a simple, "no bells or whistles" sleep and activity tracker, then the Nuband Activ+ may be the one for you. It is one of the least expensive devices on the market, priced at around $45, and we have to say, it is good value for money.

Compatible with both Android and iOS, the device is available in three colors - black, blue and pink - and has an adjustable strap.

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The Nuband Activ+ did have a problem with accuracy; it often counted normal arm movements at steps.
Image credit: Nuband

It comes with a USB charger, and it takes around 3 hours for the device to be fully powered. The battery life lasts approximately 5-7 days.

The Nuband Activ+ has a rectangular screen display that shows the date, time and charge status with the press of a button, as well as your day's activity so far. While handy, we found that the shape of the screen display did make the device bulky and uncomfortable to wear, particularly at night.

As expected for the price, the data the device records is very basic. It tracks steps taken, distance traveled, calories burned, how many hours slept and how much time was spent in deep or light sleep. It stores such data for up to 3 days before it is wiped, so you need to sync the band with the Nuband app regularly to avoid losing it.

Like the Jawbone UP24, the Nuband Activ+ has an idle alert - a vibration that tells you when you have been sitting down for too long. It also has a vibrating alarm that aims to wake you up at the best time in your sleep cycle. These are features that are not often seen with lower-budget trackers.

One problem we did notice with this device, however, was its accuracy. It often counted normal arm movements at steps, which may present an issue for those of you who want to track every inch of your physical activity.

That said, Nuband do not claim the device is all singing, all dancing. The company told us the device is an "affordable product for people getting into wearable devices for the first time," and we believe that is exactly what it is.

Fitbit Flex: good for hardcore trackers

Fitbit are a leading manufacturer of health and fitness trackers, and they sent us one of their most popular devices to test - the Fitbit Flex.

Priced at around $123, the device is at the top end of the market, though compared with some other devices in this price range, it does lag in some areas.

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Accuracy seemed to be a strong point for the Fitbit Flex. Tested with random arm movements, the device rarely registered these as steps, unlike some other tracking devices.
Image credit: Fitbit

In terms of looks, the device is strong. It comes in 10 different colors, and there are two different band sizes that both have adjustable straps. The band is comfortable to wear and is more discreet than some other trackers. However, we did notice that with continuous wear, underneath the band becomes slightly sweaty, which can feel unpleasant.

The tracking sensor can be physically removed from the band and placed into a USB charging cradle to power up. It takes around 2-3 hours for the device to charge, and the battery life is relatively short - ours only lasted 3-5 days.

The Fitbit Flex is compatible with both Android and iOS, and data from the device is synced via Bluetooth to the Fitbit app. It tracks steps taken, distance traveled, time spent active, calories burned, hours slept and sleep quality. The device works with a number of other popular apps, including My Fitness Pal and MapMyFitness.

You can set personal activity goals via the app, and white LED lights on the band show how close you are to your goals throughout the day - which we thought was a nice touch. In addition, the device vibrates when you are sedentary for too long, and it has a silent alarm that gently wakes you via vibration at your preferred time.

Accuracy seemed to be a strong point for the Fitbit Flex. Tested with random arm movements, the device rarely registered these as steps, unlike some other tracking devices.

Overall, we thought the Fitbit Flex was a good, reliable tracker suited more for those who are fairly new to wearable technology.

Misfit Flash!: ideal for sports enthusiasts

The tagline for the Misfit Flash! is "a tracker for everyone," and from testing the device ourselves, we have to agree.

We have to admit that the device is not the best aesthetically; it does feel quite flimsy and is not as discreet as some other trackers, but it does have an adjustable strap and is available in seven colors. What is more, it comes with a clasp so the device does not have to be worn on the wrist.

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One fantastic feature of the Misfit Flash! is that it is waterproof up to 30 meters, so you can even wear it swimming.
Image credit: Misfit

One fantastic feature of the Misfit Flash! is that it is waterproof up to 30 meters, so you can even wear it swimming. It can also track other activities, including tennis, cycling, basketball and soccer, so it is ideal for the sports enthusiasts among us.

When it comes to tracking sleep, the device is pretty basic. It records hours slept and how much time was spent in light and deep sleep. However, it does automatically switch between active and sleep mode, which is a plus.

Another positive feature is that the battery life lasts up to 6 months. This is because it has a coin cell battery, which does not require charging. Of course, it will need replacing once it dies, but this is easy to do.

You are probably wondering why it is called "the Misfit Flash!" This is simply because the device has a plastic disc display containing dotted LED lights. Through pressing the middle of the disc, the lights flash, indicating your activity progress.

The LED display can also be used as a watch, with the lights showing the time. This is where we encountered a problem; if you swap the disc between the clasp and wristband, it can be a challenge to work out which dots indicate what time.

The device is compatible with both Android and iOS, and it syncs wirelessly to the Misfit app via Bluetooth.

Priced at a reasonable $49.99, the Misfit Flash! was one of our favorite sleep and activity trackers.