NTT Docomo presented at CEATEC 2009 a pair of concept earphones capable of detecting your eyes' movement by measuring changes in your eyeballs' electric field.

The electric current flowing through our nerves creates an electric field that can be measured by the electrodes put inside the earphones. The software can then deduce eyeballs motion by analyzing the gathered measurements, and match it with a pre-recorded set of moves used to identify a task to perform.

In the demo, the system was getting used for navigating in a playlist and perform the common tasks you want to do when using a music player: skipping a track, pausing/resuming, changing the volume…

If you ask me, they should have hired the guy from the Osaka University who created the Mimi switch, as it's much more powerful and it's not limited to eye motion.