Computer: Rotor Power
Progression: measuring power produced by each leg independently in a crank-based power meter
Rotor Power is a crank-based power meter that not only measures right/left leg power output, it can read the negative power-resistance each leg creates during the upstroke. Although completely eliminating negative resistance from a pedal stroke may not be the most efficient way to ride, tracking it on the road could potentially help.
Rotor Power uses ANT+ transmission, meaning it is compatible with Garmin and many other computers. None of these head units can yet display Rotor’s unit measuring positive vs. negative power called Torque Efficiency. A software update coming down the pipe will do the trick.
It will sell for about $2,000 without chainrings or a computer and measures power with competitive accuracy, although their testing isn’t yet complete.