Power Meters / Powermeters (SRM, Powertap, Quarq, Ergomo, Vector, Stages, power2max, P2M, 4iii, InPower, Cinch)

@Dammit

@Greenbank took a 20 mins from within a short ride. But I see your point.

The other side being that you can't expect to hold you FTP for an hour in the middle of a longer ride - if you can, then it's not your FTP.

...unless your riding outside the hour was easy. Which is important, it makes it a practical way to test yourself on the road.