There’s increasing awareness of CycleOps PowerTap product with Team Garmin/Chipotle all riding them in the Tour de France, and the latest wheel manufacturer to offer a rear disc with a PowerTap built in is FFWD.
The FFWD PowerDisc is a full carbon “lenticular” shaped disc that is claimed to offer “the best in aerodynamics and lateral rigidity” and incorporates a PowerTap SL 2.4 hub so you can measure your awesome output.
Available in tubular or clincher and to fit Shimano and Campagnolo transmissions.