Dura Ace FC-R9100-P Powermeter

They are finally available. Shimano's first ever powermeter. And they have come out of the gate with a winner!

Shimano:
https://www.duraace.com/global/en/power-meter

Bike Radar First Ride Review:
http://www.bikeradar.com/us/road/gear/category/accessories/power-meters/product/shimano-dura-ace-r9100-p-power-meter-review-51582/

Specs:

• ±2% accuracy of strain gage measured power
• Dual Sided Measurement
• Both left and right side connected with cable
• Bluetooth and ANT+
• Simple zero reset with switch on transmitter
• Integrated rechargeable battery
• Simple re-charging
• Easily change chainrings without affecting power meter performance
• Wireless firmware update system
• Waterproof in all conditions
• Stable power measurement system at the various stepping positions
• Quick response and operation without stress; Possible to start quickly
• Direct response
• Crank arm length: 170, 172.5, 175mm (w/ chainrings)
• Gear combination: 50-34T, 52-36T, 53-39