The VSS will put out a signal that the CC can use. However, if you read the web site, they tell you that the most reliable signal comes from the magnets on the drive shaft. Bradley and I both use magnets.

If you have a stick shift with a clutch, you can also use an RPM signal, which might even be a bit smoother.

You can't use a GPS signal because it isn't reliable enough. Lose the signal - like trees, cliffs, tunnels - the CC shuts off.