i guess one thing you could maybe get away with (has not opened his wheel yet) would be to remove the locking part of your wheel. then do the cup holder idea. then a silly boy who needs crack money could get in your car and make engine noises as he turns the wheel... but he wouldnt really be going anywhere. as far as a card, you could always fiberclass around your key and make it a rather thick card ;).
again, i am not sure if this is possible, just an idea to be called stupid for thinking ;).
(if this is a great idea i want full credit and a million bucks, also someone to do the install for me ;))