Being both cheap and cynical, I'm not ready to go beyond a pedometer and try a 'fitness tracker'. I've tried Google Fit.  It doesn't work with the M8.  Something about how the sensor hardware is made. See how cynical works for you?

So I looked around, and loaded up SenseMe.  And it seems to be collecting data.  OK...

In pretty sure it's not accurate, yet, but will see.

Anyone else tried this, or some other app for the Mí?