IDEO's Technojewelry devices are appealing. There is the Penta Phone and the Ring Phone

Penta Phone and Ring Phone are concepts for mobile phones. The design takes its cue from the universal gesture for using a telephone, but is feasibly grounded in the nanotechnology research emerging from start-ups and established companies. Calls can be initiated by raising the hand to the proper position, and voice-activated interaction will allow instant communication. The little-finger units will vibrate to indicate incoming calls and the thumb unit will beam the sound towards the ear when the hand is held in the listening position.

I also like the GPS Toes a lot:

nano-derived technology, GPS Toes are toe rings that communicate to a GPS receiver kept in a purse or worn on a belt. Wearing one on each foot, the GPS Toes device will guide the wearer to a preset destination by vibrating and lighting up to signal upcoming direction changes. The left toe ring will indicate left turns and the right toe right turns, whether driving on the highway, walking on city streets, or hiking on the mountain trail.

People interested in this kind of stuff might read The experience of enchantment in human-computer interaction by John McCarthy et al. , a paper that will appear in the Personal and Ubiquitous Computing Journal