Set a variable to save the feets traveled then check if player is at start_point and set variable feets_traveled = 0, compare the player distance to the end_pooint
Then you can for add some value every x pixels traveled. Suppose you want the player travel 1 feet every 10 pixels, so set feets_traveled +=1
You would need to find the algorithm used to detect steps, probably available somewhere on Google, but I don’t think it will work if the phone is in standby (screen off in the pocket).