When will the new Fitbit activity trackers be released, and what new functions and design features will they boast? After the November launch of the Fitbit Charge Fitbit has now announced UK release date details of its new Charge HR and Surge activity trackers. Here's everything you need to know about the Fitbit Charge HR and Fitbit Surge UK release date, price and specs.See: Best fitness activity trackers 2014.

UPDATE 2016: See New Fitbit trackers rumours and release date.

Fitbit's three new Fitbit activity trackers, which resemble the Fitbit Force but have larger displays – pushing the fitness device into the smartwatch category – are the Fitbit Surge, Fitbit Charge and Fitbit Charge HR.

More: Fitbit Charge review Fitbit One review Fitbit Zip review Fitbit Flex review Fitbit Charge HR review Fitbit Surge review

Fitbit’s previous activity tracker, the Fitbit Force (reviewed), was withdrawn from sale due to a small number of users suffering allergic reactions to the nickel used on the underside of the wristband.

Here we look at what to expect from the next Fitbit trackers, when it will be available, and what it will cost.

New Fitbit Charge, Charge HR and Surge trackers: new features – Force replacement and heart-rate monitor

The Fitbit Charge is a Fitbit Force-like wristband that delivers all-day activity tracking, real-time fitness stats and Caller ID right on the wrist. It was released in the UK in November 2014.

The Fitbit Charge HR is a more advanced tracker that delivers continuous, automatic wrist-based heart rate, Caller ID and all-day activity tracking. Fitbit has confirmed that the Charge HR is now on sale in the UK online and in stores such as PC World, Currys and John Lewis. It costs £119.99.

At the top end the Fitbit Surge is a “Fitness Super Watch” that offers GPS, continuous wrist-based heart rate, all-day fitness tracking, and smartwatch functionality. As with the Fitbit Charge HR, the Fitbit Surge is available in the UK now either online or at stores such as PC World, Currys and John Lewis. It costs £199.99.

Fitbit announced UK availability on its web store on January 13, 2015.

All three wristbands from the Fitbit Charge up track steps taken, distance traveled, calories burned and floors climbed – just like the old Fitbit Force wristband tracker.

Users can tap into MobileRun, which uses GPS to track, log and compare workouts with real-time updates and voice cues to stay up-to-speed on stats and get extra encouragement to meet goals.

In addition Fitbit Charge HR includes continuous heart rate 24/7 to get more accurate all-day calorie burn, reach target workout intensity and maximise training. It offers all-day insights into overall heart health including resting heart rate and heart rate trends, alongside stats like steps, distance, floors climbed, calories and active minutes.

A bright, OLED display shows time of day and real-time stats.

Sleep detection is now automatic and monitors sleep quality using motion analysis to understand sleep and wake times; also features a silent, vibrating alarm.

New Caller ID helps users stay connected to incoming calls; the wristband vibrates and shows the caller’s name or number when a smartphone is nearby.

All the trackers are water-resistant with a new textured wristband design with an improved clasp. Previous Fitbit wristbands had a tendency to slip off the wrist rather too easily.

The Fitbit Surge – which the company is calling a "Fitness Superwatch" – has a wider and deeper screen than the Force or the Charge. It’s a tilted touch screen so you will be able to swipe through scores and fitness stats.

In addition to the Charge/Charge HR tracking features above, its built-in GPS delivers stats like pace, distance, elevation, split times, route history and workout summaries for smarter training.

It features automatic heart-rate monitoring, and can record running, cross-training, biking, strength and cardio workouts.

Eight-sensor technology – 3-axis accelerometers, gyroscope, compass, ambient light sensor, GPS and heart rate – measures steps taken, distance travelled, calories burned, floors climbed and active minutes.

It can call itself a smartwatch as it has a clock and can receive call and text notifications, as well as controlling the music you are playing on your smartphone while exercising.

The Fitbit Surge is compatible with the iPhone 4s, iPhone 5, iPhone 5c, iPhone 5s and iPhone 6 models, plus iPads from the third generation onwards. Fitbit says that it is compatible with “all leading Android devices”.

Fitbit battery life by tracker

The Charge and Surge have a battery life of up to 7 days, says Fitbit, so you can track an entire week with just one charge. The Fitbit Charge HR – slimmer than the Surge but with some of its heavier battery-eating features – has a battery life if up to 5 days. All three new models therefore require more frequent charging than the existing Fitbit One tracker which lasts roughly two weeks.

Top 10 tips for hitting your Fitbit step goals

New Fitbit tracker release date

The Fitbit Charge is available from November 17, 2014 on Fitbit.com and in leading retailers nationwide.

The heart-rate trackers Fitbit Charge HR and Fitbit Surge will be available "broadly" in early 2015 said Fitbit at the end of 2014. We now expect to see the Charge HR before the end of January, and the Surge maybe a week later.

Next-generation Fitbit Charge, Charge HR and Surge activity tracker UK prices

The Fitbit Charge costs £99.99. In the US it costs $119.

The Fitbit Charge HR is £20 more than the entry-level tracker, at £119.99 (US$149).

The Fitbit Surge is priced at £199.99 (US$249).

New Fitbit Surge, Charge tracker colours

The Fitbit Charge is available in black, slate, blue and burgundy.

The Fitbit Charge HR will be available in black, plum, blue and tangerine.

The Fitbit Surge will be available in black, blue and tangerine.

New Fitbit Surge, Charge sizes

The Fitbit Charge, Fitbit Charge HR and Fitbit Surge will be available in small, large and extra-large sizes; the extra-large size will be available only through Fitbit.com.

Fitbit PurePulse heart-rate technology

Fitbit Charge HR and Surge feature Fitbit’s proprietary PurePulse optical heart-rate technology, which provides continuous and automatic wrist-based heart rate tracking, without the chest strap usually required in products such as the Polar Loop and its compatible heart-rate sensors.

PurePulse uses LED lights to detect blood volume changes when your heart beats, right on your wrist and applies Fitbit’s algorithms to deliver heart rate tracking 24/7.

According to Fitbit PurePulse helps users:

• Get accurate calorie burn for more activities – during exercise and everyday activities like walking, running, biking, lifting weights, spinning, skiing, yoga, Pilates and more.

• Maximise training with fat burning, cardio and peak heart rate zones.

• Maintain workout intensity by reaching your target heart rate.

• Optimise health through heart-rate trends and resting heart rate, an important measure of overall heart health and cardiovascular fitness.

Fitbit One review

Fitbit Zip review

Fitbit Flex review

Fitbit Force review