As communications systems increasingly gather and propagate information
about people�s reachability or �presence�, users need better tools
to minimize undesired interruptions while allowing desired ones.
We review the salient elements of presence and availability that
people use when initiating face-to-face communication. We discuss
problems with current strategies for managing one�s availability
in telecommunication media. We describe a prototype system called
Lilsys which passively collects availability cues gathered from users�
actions and environment using ambient sensors and provides machine
inferencing of unavailability. We discuss observations and design
implications from deploying Lilsys.