Clifford (well any DEI system really, same as Viper) RSX Matrix 3.5 for sure. I have the older version of this in my car and I love it, insane range. No problems reaching the parking lot from inside a department store. It's a little spendy, but if you get the parts on eBay and install it yourself it's not bad.
Oh, it has remote start and turbo timer built in. Several options too, such as a trunk release for the pull cable ones like DSMs, automatically roll up the windows when you lock the car, proximity sensor if you want, so many things you can do with it.
http://www.clifford.com/matrix/responder/default.asp
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