Any of the alarms/starters made by DEI inc will work with the alero, you just have to get the Passlock bypass module to go with it.
This guy sells on e-bay, I got my set-up from him.
http://www.asianwolf.com/caralarms.htm
Check out th eValet 554R, it's the updated model of the Hornet alarm I bought last year, great alarm/remote starter!!!!!