Security tokens are pretty common these days. You know the kind: A credit card-sized piece of plastic with an RFID chip and maybe a magnetic strip to boot. Touch and go! But besides the credit card form factor, are they actually practical? They are brittle, and they can't be attached to anything without drilling (which would make them even more fragile). Here's an idea: Get a small RFID chip, and put it into a small piece of ABS plastic with a metallic ring that goes into the middle of the ABS and extrudes just enough to include the whole thing on a key ring (see below). Now if you have an RFID reader somewhere on your desktop, it should be enough to sit close to the desk for it to read the chip. So you won't end up with a broken card, you won't have to put your entire wallet (or some other container) in your pocket to protect the card, and you won't have to leave it on the desk at all.

Security token schematic

PS: Is it possible to make stuff like this (with embedded metal, and without destroying the chip) on a 3D printer?