iPhone ringer

Like millions of others, I cut the cord and ditched my landline telephone. It had progressed to the point where I simply never used it. Do t miss it, but aside from the voice quality (landlines sound better) the one thing I do need is a house wide ringer. If I leave my iPhone in the pocket of my coat, I might not hear an incoming call upstairs. So, it would be kinda cool to have an app or program on the Mac in the house that detects the nearby iPhone and send a ring out to the AirTunes speakers.