After suffering from a severe disease like spinal cord injury or stroke, patients are often unable to interact or even communicate with their environment anymore, especially at the beginning of rehabilitation. Brain-computer interfaces (BCIs) can substitute these temporarily lost communication channels. They also might support rehabilitation by providing an alternative way to control a computer: by thoughts without any muscle activity. This enables the patient to communicate by writing letters on the screen, and stay in social contact with friends or people outside of the rehabilitation facility by participating in games like Second Life^© where they may appear as healthy people. Another application is to control items in their room that are connected to the BCI system, like the lights, which can be turned on and off (as can be done in a virtual smart home without leaving the bed). In this paper, the technology of such BCIs and the mentioned applications are described utilizing the P300 approach. A generic BCI interface is presented which allows concurrent control of the different applications and the ability to switch transparently among them. The results of a recent study show that a BCI can be used by patients suffering from cervical spinal cord injury almost as well as by healthy people. This encourages us to think that by enabling the user to socially interact and communicate easily, these applications may assist in rehabilitation and slow down the progress of late syndromes.