The RoadID ones also have the option of paying them a yearly fee to have all your details held on their website, and only accessible to someone who telephones or logs into their site. Not completely thief-proof of course, but having to call/log in would probably deter most casual thieves.
I can't remember for sure, but I think the fee for that is about $10 per year. Also gives you the ability to log in to the RoadID site yourself and update/change details as required, for example if you're going on a business trip or a holiday you can temporarily change your address, contact details etc or put on the address of the hotel you're staying at, that sort of thing...