How to unlock a door...

1. Purchase a Basic Stamp 2, and a RFID Reader Module. You'll also want to buy a bunch of RFID tags.
2. Go to your local hobby store, and purchase a reasonably strong servo. About 51 oz-in should do the trick. I used the Futaba FP-S148, which is available for less than $20.
3. Purchase 4 packages of 3M Command Adhesive Wire Guides at your local hardware store.
4. While you're at the hardware store, buy a flat aluminum bar, some #8/40x2 1/2 machine screws, matching nuts and washers (you'll need three nuts) and a replacement wheel for a shower door. Cut the bar down to 6", and drill holes in it (1/16") to correspond to the screw holes in the servo horn. Drill holes at the other end with a 5/16" drill (same size as a #8 machine screw) at the right place so that the wheel will barely touch the deadbolt latch when it first reaches it. Sorry to be so imprecise, doors and measurements vary wildly.
5. Attach the bar to the servo with small screws that come with the servo, the shower door wheel to the bar with the #8 screws and nuts (see detail on flickr page), and the servo to the door with as many command adhesive strips as you can fit (they release with shearing force).
6. Drive your wife crazy by wiring up the door.
7. Customize and upload This program to the Basic Stamp.
8. Enjoy.

(edited to add some detail)
(edited again to disallow comments, since the spammers seem to have found it)