I think, therefore I am logged in.

Wired:

"Researchers at Carleton University in Ottawa, Canada, are exploring the possibility of a biometric security device that will use a person's thoughts to authenticate her or his identity.

...Their idea of utilizing brain-wave signatures as "pass-thoughts" is based on the premise that brain waves are unique to each individual. Even when thinking of the same thing, the brain's measurable electrical impulses vary slightly from person to person. Some researchers believe the difference might just be enough to create a system that allows you to log in with your thoughts."