This is the new GS model in 2017. This brand new model is universal for rear derailleurs as well as internal gear hubs (including Rohloff and NuVinci hubs).
The Gearsensor acts like a speed shifter so you are able to shift your bike at full throttle and barely fill the throttle cut off.
It will make your BBS02 or BBSHD shift faster, smoother and safer.
Here is a link to the manual and installation guide on the Gear Sensor
The Gearsensor is plug and play with any BBS02 or BBSHD in place of one of your ebrakes and is a 15 minute install.
If you install it with our newest edition of BBS02 or BBSHD (the ones with the luna cycle logo engraved on the side) the controller has a separate ebrake connector so you can use both ebrakes and the gear sensor. If you go with this setup the shifting power delay is much shorter than using the ebrake connector.
However the gear sensor will work with all bafang mid drives by simply connecting it to one of the ebrake cut off switches. It will also work with any mid drive equipped with an ebrake cut off as long as the user can rewire it to fit their ebrakes.