This nifty multi-function watch from ThinkGeek not only good for making/receiving calls, but "but you can also play MP3 files, watch movies, store hundreds of phone numbers and send SMS messages and enter schedules or notes with basic handwriting recognition." Video after the break. Click here for one more picture.
Just pop your existing sim card out of the top of your iPhone (or other GSM Cell Phone from AT&T/Cingular or T-Mobile) and insert it into the back of the watch and power it up. Call your standard cell phone number and your wrist will start ringing