Pebble has announced an update to the humble Pebble, its first generation smartwatch, appropriately called the Pebble 2.

In many ways the Pebble 2 reflects the Pebble heritage, offering many of the same features and functions. But with a new focus on giving you a connected fitness experience, we've drilled through the details to sort out what's what.

If you're wondering what the difference is between the Pebble 2 and the original Pebble Classic, then read on.

The original Pebble was notable for its fun plastic build. The Pebble 2 continues the cute story with a polycarbonate (plastic) body and a 22mm lug for the strap. It comes in five colours: black, white, aqua, flame and lime and measures 39.5 x 30.2 x 9.8mm, not including the lugs. The Pebble 2 weighs 31.7g.

The Pebble Classic also has that polycarbonate body and comes in black or red/black currently, although other colours have been available. The Pebble Classic measures 52 x 36 x 11.5 (including the lugs) and it weighs 38g. Again it offers a 22mm width strap. 

The Pebble 2 has slimmed down, lost some of the bezel, for a more compact and lighter device, but the original Pebble was water resistant to 50m, now it's water resistant to 30m in the Pebble 2. 

The Pebble was notable for its use of the E-Paper display, meaning much less battery drain than LCD smartwatch rivals. That's not changed, with E-Paper still the display of choice on the new Pebble. 

The Pebble 2 has a 1.26-inch display with a 144 x 168 resolution, sitting under Gorilla Glass 3 to keep it protected. It is black and white. If those specs sound familiar, that's because it's the same as the Pebble Classic, that also has a 1.26-inch E-Paper display with 144 x 168 resolution. 

No change there then: if you're a fan of Pebble, at least the display won't have changed much. 

When it comes to the hardware, the Pebble 2 comes with an ARM Cortex M4 processor, whereas the original has an ARM Cortex M3. The M4 was in the Pebble Time previously, so is likely to give a slight boost in performance over the original model. 

Pebble is all about battery life - especially when pitched against Apple Watch or Android Wear - and the Pebble 2 offers 7 days of battery life according to Pebble's stats. The Pebble Classic offers 7 days of battery too, so we'd expect a similar experience.

There's a big change on the hardware front though with the inclusion of an optical heart rate sensor on the rear of the Pebble 2. The old Pebble doesn't offer this function. Both offer Bluetooth, but there's no Wi-Fi or GPS on either.

As our comparison of the hardware revealed, the big difference in features between the new Pebble and the old is going to be heart rate tracking. 

Pebble 2 is now a bone fide fitness watch, offering to keep track of your steps, sleep and heart activity, using Pebble Health to collate your details. 

The original Pebble offered apps for sports, but lacked the hardware for your heart rate, although it offered sleep and activity tracking. The Pebble 2 is definitely going to be an enhancement for sports fans. 

The Pebble 2 will run the latest version of Pebble OS, with over 13,000 apps available.

The Pebble 2 very much sticks to the premise of the original Pebble it now betters. The design is more advanced, making better use of space, while adding the new heart rate sensor on the back. 

That means the new Pebble 2 will expand its feature set and appeal to those interested in keeping track of their fitness, but the experience is likely to remain fairly close overall. At the end of the day, both the Pebble 2 and the Pebble Classic offer a compact black and white display in a polycarbonate body, bringing connected features to your iPhone or Android device through a range of innovative apps. 

The original Pebble is currently selling for £79.99. The Pebble 2 will sell for $99 (£70) on Kickstarter, with the standard retail price set to be $129 (£90).