My aftermarket JVC in my old 240sx had it. It went by the sound of the engine as your RPM'* went up, it got louder. You could program it by sitting at idle and press a few buttons. No hookups necessary. Magic I tell ya.
It'* actually SCV not SVC. Speed Compensated Volume. My 04 Cavalier has it and you can actually set the gain. There'* high, medium and low. I keep it on low because, still being new, I don't get much engine or wind noise...yet!
My old 97 Cavalier actually had the exact same setup too. Personally, I've always liked it. It did take some getting used to, though.