A friend and I actually wrote this exact service, you'd get a number and forward it to whatever, and depending on the who was calling and when (with some rules you would set up), they would either ring through, be prompted that you are busy/sleeping/meeting, or go straight to the cellphone voicemail.

The problem is cost. ALL calls would have to go through this system, (which have a per-minute cost if they aren't over VoIP), so our minimum monthly price for this servce would probably be $15+.

Do you think you would pay that much? Most people loved the demo we showed them, but were hesitant to pay more than a few bucks a month. But, if you think differently I'd love to hear more.