One of my collaborators on OpenBCI is Conor. He's done some really cool EEG hacks. This one is really sweet:
It uses a Neurosky Mindflex, an Arduino, and a Sparkfun bluetooth module. It monitors his brainwaves, analyzes the energy content in different frequency bands, and sends the data out over Bluetooth to his Android app. The Android app that he's using (did he write it or use an existing one?) looks like:
With this app he can log the EEG data along with his mood and activity at the time. Through post-test analysis he can look for correlations.
Overall, this is a sweet project. I'm looking forward to stealing...I mean, borrowing...I mean stealing his ideas for my own hacks.