EEG, or Electro-Encephelo-Graph, (literally: the reading of brains electrically) is a means of scanning the electrical activity in the brain, usually for medical purposes. Devices can do it, but as medical devices, they come at a premium. After all, you only get one brain, and it's not like you can go out and buy another if you fry it. So the device is built to very exacting specifications.
A group called Open EEG has an EEG hardware and software system for scanning your brain electricity that you can build yourself, or, alternatively, order from Bulgaria. The hardware connects your brain to your computer, and the software analyzes the output. Having this knowledge, most people are then able to control their brain output via a biofeedback process.
Hypothetically, one could go on to do Mindtyping, therapy, or something else, but that hasn't been written yet.