>From NewScientist, 29 March 1997, page 26, PATENTS:

Tattoo timepiece

A programmable tattoo is being patented by Interval Research of Palo Alto,
California (WO 96/39977). A small liquid-crystal display is inserted just
beneath the skin on the wrist, where most people wear a watch. Because
human skin is partially transparent, the display is clearly visible.

The display is connected to a control chip and power comes from a small
battery. Both of these are implanted beneath the skin. Implanting is an
outpatient operation and the battery can be recharged inductively, by
holding the wrist near a charger.

As well as being a fashion accessory, the tattoo could contain biosensors
to monitor temperature and blood pressure, and display these readings--with
a clock showing the time.