best device to count calories burned when exercising please?

I have the Garmin Vivoactive HR and have been very happy with it. There are accessories like chest straps that can be used with it if you need more accurate or detailed information.

I use a Samsung Gear S2.

The problem with the Gear S2, Fitbit, or any other type of wrist worn device is that it only tracks your movement so long as that arm is in motion. If it's not moving (or not moving fast enough to be detected), it won't register the motion.

The best apparatus I've seen is actually the EA Sports Active peripheral for PlayStation 3. It's 2 wrist monitors and 1 ankle monitor. The system reads the feedback from all 3 to get a more accurate measure. The problem is that this is only compatible with the EA Sports Active games.

All of the above will measure your pulse. Later models of Fit Bits and the Gear S3 do a much better job of measuring your pulse more accurately.