I suggested this to friend for his new at the time 2007 GMC Sierra reg cab shortbox Z71. he had 26" rims on it and it was a thief magnet. He had a 2 alarm systems on it, 1 would dial his cellphone.There were 3 attempts to steal it, they defeated the alrm systems but couldnt couldnt get it started due to the Ravelco. The 4th attempt he forgot the little grey connector that is the "key" to the system in the truck, so this time they started it up and drove it away.
It works, but only if you "arm" the system by removing the grey key..
He had a local stereo shop install it. The grey key becomes part of the cars electronics so if the "key" is removed, a lot of circuits are incomplete. Supposedly if a thief tries to back probe where the "key" socket, fuses will short rendering the vehicle undriveable.
There was a good write-up a few years ago in GM High Tech Performance.
http://www.ravelco.com/
peace
Hog