[rjk909]

If you're looking for an idea for a pro feature, have users calculate their stride length (they'd need to run say a mile and count their footsteps)

then convert that to a tempo in BPM for a desired speed (that's like a five minute math problem there, to quote my math profs, it's an exercise for the reader)

then play songs within 5% of that BPM.

Boom. Pace yo self.

[aquark]

This would be very interesting to try -- I don't trust the GPS accuracy of my phone over short distances, so using GPS to detect pace changes could be error prone.

As an extra advanced trick: adjust the stride length for incline changes ... though I don't know how you get that information accurately enough!

[vinnycoyne]

BPM is something I'm very interested in playing around with!