There are some EEG (Electroencephalogram) devices that allow one to map the EEG signals (or some function of them) into MIDI data (note, velocity, controllers, etc). This MIDI data can be routed to your host sequencer (Sonar, Project-5, Cubase, etc.) via a MIDI loopback device such as MIDI Yoke. This way, you can just place the electrodes (EEG sensors) in your head or body, set up the EEG software to map the signals into MIDI data, and play your synths with your brain (look ma, no hands!).
One of these devices is the
Mindpeak WaveRider. The software looks like this:
In this picture you can see the raw EEG signals for two channels (top-left), the spectrum analyzer (top-right), the average power of the signals in the alpha band (8-12 Hz) (bottom-left), which is being mapped to MIDI note and velocity (bottom-right). Just for the sake of the example, I ran the MIDI output through the internal soundcard's GM synth and recorded the resulting sequence as audio. You can listen to it
here.
Unfortunately, I don't have the device here with me, so this sequence doesn't come from my own brain, but from pre-recorded signals. But the program does work in realtime. It sure is more fun than entering notes with your mouse.