Yes, the Stages Cannondale Power Meter is compatible with the Cannondale One crankset. It is also compatible with 2014 or newer Cannondale Si, Hollowgram Si and Hollowgram SiSL2 cranks. Please note that the shape of the Stages power meter is a bit different than the Cannondale One crankset, which is a cosmetic difference only.
Please also note, these power meters attach a sensor to the inside of the left crank arm. On some bikes, there is not enough room between the left crank arm and the chainstay for the sensor to clear the frame. Therefore, you should make sure you have at least 10 mm of clearance for Stages power meters. Also, please make sure that you don’t have a bottom bracket mounted rear brake (used on some aero and TT bikes). Please refer to the image below.