i totally like this idea! would definitely use it if such a tool makes it's way to our n900
...and yeah maybe it's like using a shotgun to kill a fly - but to me forwarding the call and then handle it elsewhere looks like using a shotgun for that with the need of shooting twice :P

the "problem" with just rerouting the call (no matter how) is that the caller hasn't the chance to let you know this call is very important and he want's to talk to you no matter what you are doing at the moment...