I bought and installed a Viper 3100 alarm system It seems to be a nice unit, not very expensive and ALMOST all the features operate.
But BE AWARE/WARY The KEYLESS ENTRY FEATURES DO NOT WORK ON 12 VDC DOOR ACTUATORS.
Before buying a keyless entry system make sure that the unit outputs +/- 12VDC. All the ones I found output a +/- 5 VDC signal