I'd seen a neat idea where a cloud shaped key holder used magnets to hold a bunch of keys decoratively on the wall (kudos due here: http://www.suck.uk.com/products/cloud-keyholder/?search=cloud). The only problem with that solution is that at home we don't keep our car key fobs on a ferrous keyring and since the metals in the fobs themselves are non-magnetic, we needed a little pocket in the back of the cloud.
Printed on a RepRapPro Mendel in PLA. The bottom slot is for some ebay sourced cuboid (30x10x3mm) rare-earth magnets. The curved slot above the magnet slot is for some optional metal shielding/redirection for the keyfobs (http://www.kjmagnetics.com/blog.asp?p=shielding-materials. A quick google search did not determine if magnetic fields could actually damage a cars keyfob). The keyfob shelf is big enough for either a VW keyfob, or a Volvo one so I suspect most keyfobs will fit (I don't own enough vehicles to test it with more). Cloud can be mounted either with double sided foam tape or with a pair of nails (or both as I have done.