Yet these systems are still curiosity of laboratories, them announce a quantum leap forward, for the disabled.
In the US, the NINDS has an active research program on this field. See for example this video of the BrainGate system, shot in the Massachusetts General Hospital. It helps understanding how promising this technology is for tetraplegic people.

Behind these devices, there are a lot of software. Given the high complexity of the technical problem, a few research teams developed framework solutions, like BCI2000, BF++, and OpenVibe, developed by a research laboratory of INRIA.
Openvibe is available under LGPL license and easy of access with graphic programming. If you're channelling the soul of a brain computer interface designer, you can download it and start developping the next generation of medical device!