here's the thing...
There is no perfect device. There are always trade offs... Hence there is no 'BEST' device for the world, only which device is best for you. You can't have awesome battery life, a touch screen, android wear support, and gold plate it all for under £50 /$50....
And in the absence of any particular information about what you want, Its really hard to recommend something.
I'd suggest that you should go and do a bit of research about Android Wear, Pebble Devices, and also other activity trackers such as Jawbones or Fitbits....
All of those will sync well with your devices, but have different focuses and feature sets...