Scientist have found a way to talk to all those in a vegetative state, however it is very much a yes or no conversation however it offers new hope to patients, friends and relatives. Although this is not completely new, it uses MRI to see brain activity, the patient is told to imagine playing tennis as yes and not as no. The MRI detects activity in the pre-motor cortex.

http://news.bbc.co.uk/1/hi/health/8497148.stm