Years ago the first mod to my aveo was cruise control. I bought a control from Rostra Precision Controls in Laurenburg NC (way cool it was an NC company and I was living in Raleigh). It looked like this:
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The wireless controller clipped on to the steering wheel and it really does look seamless. I have been very happy with it sense. I went back and there are no longer offering that option. Basically it just sent a can bus message to set the speed to the computer.