What kind of car? Ive always had Avital (made by DEI who makes Viper). They are easy to install yourself with the proper wiring diagram. Not sure Id want to install one in a new car now-a-days.
I installed an Avital remote start, keyless entry in my 99 Explorer a few years back and it took all of a afternoon to do so.
These are nice for the price and have a long range.