Could microdisplays (see http://www.microdisplay.com) be fitted into mood rings and turned into cellular videophones w/MEMS identification?
How could such a device be powered so that it still had a low profile on the wearer's index finger or thumb?
What kind of range could a MEMS-based two-way telemetry system have if this were to be used as a passport/wallet/micro-cell phone?