ThinkGeek offers the NeuroSky Mindwave Brain Waves Sensor for $55.99. Coupon code "FRACTAL" cuts it to $41.99. With $6.95 for shipping that's the lowest total price we could find by $31. Plus, get this ThinkGeek Holiday Meh T-Shirt for free when you add it to your cart and apply coupon code "STRIPED". It's purported to "exercise your mind" and features a wireless EEG headset with passive sensors and wireless USB adapter. Deal ends today.