Withings released its Pulse tracker late last summer, and now the outfit has announced it's successor: the Pulse O2. Just like that first fitness gadget, the new model keeps tabs on heart rate, sleep and activity (steps, distance, elevation and calories), but it also keeps an eye on blood oxygen levels with a lens and light mounted on the unit's back side. While you might not find that a useful bit of info, mountain climbers and folks who suffer from breathing problems -- like asthma -- need the data to monitor respiratory function. The Pulse O2 automatically syncs in the background thanks to Bluetooth Low Energy and Withings has added real-time coaching to its Health Mate app for a bit of added motivation. And as you can see in the image above, there's a new wrist strap so you can sport the Pulse O2 like a watch, if that's your preferred method of wear. Sound too good to pass up? Well, the wearable is on sale now for £100 ($120).