Here is a smart armband that you can wear to keep track of your fitness training sessions. The TICKR FIT Optical Heart Rate Armband provides you with heart rate and calories burned on your phone. It comes with Bluetooth and ANT+.
This wearable device has a battery that lasts up to 30 hours. It comes integrated with Apple Watch and Apple TV. You can use this with third party apps like Strava, Runkeeper, and MapMyFitness.