Those after torque proportional pedal assist systems now have a new plug-and-play option available. The bottom bracket sensor from TDCM uses novel geometry to measure the backwards chain force on the cranks rather than the spindle torque in order to sense your pedaling force.
This enables it to sense both the left and right pedal effort, giving a more immediately responsive PAS system at a much lower cost than magnetostrictive torque sensors. On the other hand, it is not as accurate at measuring human watts as the THUN sensor, and the installation is a bit more complicated as well.
We have the TDCM units custom made to run directly off the 5-pin V3 Cycle Analyst plug just like the THUN sensors, and have these new pedal sensor options available in the CA Parts page in 114, 120, and 128mm spindle lengths. The TDCM is a better option if the main goal is proportional pedalec assist, while the THUN unit is best if accurate human power output is needed, or if the chainline is not perpendicular to the legs (e.g. recumbent bikes)