Originally Posted by WalksOn2Wheels

I could be very, very wrong, but it would seem to me that if we're talking about differential air speed, we also need to factor in frontal drag. That's too individual from person to person and hugely individual from sitting up vs. tucked into an aero position. I mean, maybe they have an assumed coefficient that is average enough to give close enough numbers for 129 bucks, but we'll see.

Isn't there a handlebar mounted power meter that does sort of the same thing with airspeed? Perhaps they happened upon a more accurate algorithm by placing it on the valve stem. Sort of a reverse brake dyno based on airspeed. Interested to hear more.