i have accidentally activated the fitness tracker app on my phone and was wondering how the step counter worked. Does it detect side to side motion and assume walking and estimate steps (my phone is generally in a handbag rather than a pocket) or is it using GPS to measure distance travelled and estimating average step count from that. All it does is nag me. I can't have my phone on me at work so it doesn't count me walking round my lab - I rarely sit down - and works only intermittently when I am cycling. On Sunday, I went for a 2 hour bike ride (phone in pocket, not handbag!) it told me I had been for a 20 minute walk!