Mobile devices allow diverse groups of people from all along our social graph to contact us wherever we are, but offer only rudimentary ways for us to control our contactability (toggling between available or unavailable). As mobile devices play a bigger and bigger role in our lives, I believe we'll need to add more control/granularity to this experience. In this sketch I propose a more probabilistic way to manage contactability - a kind of semi-permeable barrier with rules we can tweak and change to suit our lifestyles. Contactability as probability.