Bulldog alarms are pretty nice...they sell them at Wal-Mart and you can install them yourself //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
dont waste your time with anything but a directed made, that would be a viper, clifford avital pyton and more. They are hands down the best around.
I would look into the 771xv, 791xv, or 5900 sst by viper. They are great alarms, i install at least one a week.
That is your other problem, you need it installed which is not cheap, you can get it done cheap but an alarm is not something you want to skimp out on.