And really, who doesn't want another way to skin a cat?
As for what you're actually doing: I think the hard part will be manipulating the mic/input side of things while the default Nokia phone app is running so people don't hear a second of whatever's going on on your side. A second may not seem like much, but just image if that ring picked up just in time to hear: "<ring> OH! Yes! Bab... <click> I can't come to phone right now. Please leave...."