Well after reading this thread it appears there is no useable "VSS" signal available on a 1200GS. Sad because on other bikes I've installed the Rostra and the VSS signal was so slick! (ie Concours 14). However on my R1150RT I had to implement magnetic coil pick-up and put small neodym magnets in the bolts heads of the brake rotor attachment bolts. Works very well. Just a bit of a pain but well worth it.
I have gotten so spoiled to using an electronic cruise over the past several years of riding that a recent trip on the CDT (the return trip was all SLAB) I went nutz having to hold that throttle with nothing more than a Kaoke for 1700 miles back to the house. I gotta get some relief so I am going through the PITA
of installing a cruise on my GS.
If any of your tech whiz types figure out a way to tap the ABS wheel ring pulse such that the Rostra brain can decipher it please post it here. I don't THINK I saw any solution in this thread. But if I missed it please point it out.