[flakeoil]

Please, not too many sensors. Long battery life and small size and low weight is more important. All the other smartphones and fitness watches have these sensors so get one of those instead.

Maybe a HW interface to attach other sensor modules could be an option, but could also easily become a distraction and pull down the overall experience.

[Edit] A wireless i/f (bluetooth, LP RF) is of course better to use as interface to any peripheral sensor modules.

[gvurrdon]

A Pebble 2 HR with a colour screen would do the job for me, I think.