What is the X in X-mas?
A pointing device (unlike a mouse in design, but serving the same purpose) which works via sensors in contact with the user's skin. The sensors are built into a plastic base which fits on one finger and which is similar in shape to a finger cast.
The principle of operation is presumably myoelectric, not psionic, contrary to what the name implies.
As of the time of writing (1996), mind mice are not accurate enough to be anything but novelties.