ZWATT is not a power meter as such from what I can gather. Instead they make the electronic power meter bits that they integrate into other equipment manufacturer’s parts.
So, for example: the nattily named SG6x has been recently integrated into crank arms; the SG5x into spindles; and the SG7x into a spider. They also have an in-frame cadence sensor.
Their website seems to suggest that they will only ever integrate with other manufacturer’s components rather than selling to the general public.
In exchange for your data it seems they want some help with testing. Anyway you can sign up <here>. Can’t hurt.
Some techie bits on their capabilities:
•Left Pedal Smoothness
•Left Torque Effectiveness
Compatibility with Head Units
•ANT+ power meter profile compatible with modern bike computers supporting the ANT+ Device Profile – Bicycle Power
•Bluetooth Smart power meter profile compatible with smartphones (for Strava app etc.)
•Spin crank to turn on – calibrate on head unit (when needed) – ride
•Recharge every ~400h (depending on battery selection)
•Weight: 18g (depending on battery selection and installation options)
•Temperature: -10C to +50C
•Accuracy: +/-2% (@200W, 90 RPM)
•Principle: Strain gauge measurement of arm
•Wireless firmware upgrade
•Simple head unit bike computer (Cadence, Power, Left Pedal Smoothness, Left Torque Effectiveness). Customized on request.
•iOS and Android
•No wires, zip-ties, magnets or additional hardware to install
•Factory installed and calibrated