A friend and I were discussing what I should do for the Hackathon. He jokingly said "you should control LEDs with your mind! I accepted the challenge and wanted to see if I could.
I also wanted to start getting into Wearable Hardware, so I figured it would be cool to make them wearable LEDs.
What it does
You wear the Mind Wave headset and an unconnected T-Shirt with Flora LEDs sewn into it. The color of the LEDs will vary from Green to Red depending on Relaxed (Green) or Focused (Red) your mind is.
How I built it
The headset came with a USB RF Dongle for interfacing with a PC. I made some hardware modifications to the RF Dongle to redirect the communications to an Adafruit Flora (Wearable Arduino). I wrote an Arduino Sketch to control the RF Dongle based on Neurosky's documented protocol  and a guide on their Developer Wiki . The Sketch receives periodical updates from the Dongle as to the wearer's meditative and focus levels, and varies the colors of the Flora LEDs based on them. I also added a chain of 4 Adafruit Flora NeoPixels to add to the effect. All of this was sewn onto the Hackathon 2015 shirt!
I did do research related hacks that some other people had done with the Mindwave headset beforehand to get an idea what I was in for. Special thanks for a wealth of information that helped make this possible. I referred to the following resources:  http://www.instructables.com/id/Build-an-EEG-hat-that-turns-your-brainwaves-into-l/  http://developer.neurosky.com/docs/doku.php?id=arduino_tutorial  Neurosky Developer ThinkGear Serial Protocol Guide
Challenges I ran into
Number 1 challenge was sewing! Sewing is hard!
I ran into a lot of power related issues--because I am not using the USB on the RF Dongle, it needs to be powered from the Flora system. This plus the Flora plus 4 NeoPixels apparently was too much for the standard Flora power system.I had to to cut out 2 of the NeoPixels to get it to function again, and it is still a little flaky. Given more time, I would be looking to set up a beefier battery-based power system that could sufficiently support everything.
Electrical signals emitted from the brain are very subtle and can be difficult to reliably read in noisy environments. I had to leave the DHF and do some of my work at home because there was too much activity in the air.
Accomplishments that I'm proud of
Learning to sew! Doing a hardware hack without [completely] destroying a $80 piece of hardware. Getting to play with wearables. Having the coolest shirt at the Hackathon! Met a bunch of cool knowledgeable people.
What I learned
I learned to sew [kind of]. Learned a bit about brain control interfaces and wearables.