I've got a viper alarm in my truck... its pretty nice cant complain. I can do a silent arm/disarm by pressing a second button on my remote and then the alarm button.... a nice feature when you come home late and dont want to bug the neighbors 
If you're refering to additional relays and such to control extra features, then no, I didn't need to buy anything in addition to the system. It seems, judging by the different alarms I looked at, that most these days already have the relays built into the main CPU. But there are some features like window roll down and what not that may require an extra relay if you want it. All the main features seem to be covered in the standard system (door switch, trunk switch/hood switch, siren, lite flash, impact/shock sensor).TOYMAN321 said:Marblehead, did you need any additional parts that didnt come with the viper system????