A gate keeper application which could block or allow calls through based on caller, urgency, and activity. For example, a religious individual could have one setting for prayer, one for sleeping, and one for work meetings. The contacts allowed to interrupt each activity would be preset, as well as the level of urgency required to put the call through. Urgency could be indicated using a scale of one to nine and a custom message could accompany each activity.
The fine tuning would be very specific. For instance, unknown callers could be allowed through during certain activities while a selection of your contacts remained blocked, and a separate message could be played for each group; the unknown callers, the blocked contacts, and the allowed contacts.
Alternatively all blocked callers could be sent straight to voice mail / answering machine as if the phone was off / in use, and even the answering machine could be blocked for certain callers based on certain criteria. For example, anyone leaving a second message before you have listened to the first could be subjected to a confirmation that the new message contains new information to prevent certain personalities from leaving a half dozen identical messages.
This entire system should also be able to extend from phone calls to all forms of incoming communications.