Mult problems with this type of system
First off and auto security system will have to have a bypass or reprogramming mode for service or if you loose the key you have to throw away the car, if there is a reprogram or bypass mode that more than 1 person knows about it'll be on the internet in short order like the software key code crackers. Walmart is pushing the development of RFID for it's stores so that a customer basket can be scanned in mass rather than one item at a time. They were lucky enough to find out that their development was looking at a problem. There is already a scan and reprogram device (about the size of a small calculator) that can change a $37 ham to a $.98 curtain hook. Imagine the havoc that a person with a grudge against Wally world could inflict by randomly reprogramming the tags in a store they would not even have to buy the item just wait for a completely innocent person to put it in their cart. Good thing everyone loves Wally World. A now defunked Chevy dealer in Memphis had a inside man copy the keys for cars in for service and giving them to his buds with the address so the cars could be easily picked up later. The insurance companies know these devices exist but jerk you around on the claims to try to reduce the payout and then wonder why a jury will award huge damages against them, try to find 12 people that don't think they have been screwed by and insurance company over something. Good Luck!
-v mode again