I have placed that tab on the other side too, and they are both for VR sensors.
The sensors pick up the heads of the cv bolts and pulse 6 times for every revolution of the wheel, so I know how fast the wheel is turning. I am programming an AVR microcontroller to interface to the S60Pro ECU and feed the data from the ECU, into innovate motorsports Logworks 3 data logging software. I have a bunch of other innovate stuff as well, so I am incorporating all of the data into a nice 7" TFT touch display on my dash
I can then log both rear wheel speeds, and compare that to the front wheel speed to see how much wheel spin I have when driving.
This will tell me if I need an LSD or not
BTW, the S60Pro has a traction control setting that uses the undriven wheel speed, gear setting and engine RPM to determine wheel slip and retards the ignition to keep traction
Lanner is machining my front hubs to use the 944 antilock rings that come stock on the hubs so I can play around with this feature.
Sandeep