We summarise the results of the first studies to investigate the Cyberlink brain body interface as an assistive technology. Three phases of studies and a contextual inquiry were performed with a range of users. A focus group was formed from brain-injured users with locked-in syndrome who have no other method of communication or control of a computer than the Cyberlink. Versions of a Yes/No program were then created to allow communication and have achieved some success with the focus group. The purpose of this paper is to discuss how this program has been improved and what steps need to be taken to create communication programs for persons with severe motor impairment. As a result of our experiences, we have been able to develop a set of design guidelines for brain-body interface operated Yes/No programs. These are presented and justified on the basis of our experiences. We also raise some general issues for assistive technologies of this nature.