Cory Doctorow featured a distributed excuse network exactly like this in his short story I, Robot.

You can read or listen to the podcast of the story for free here:

http://craphound.com/000189.html

In Doctorow's version, you called the number, said what you wanted said, specified who should say it (adult male, etc), and what number they should call. Once in a while, you got a call to do the same.

There's nothing to stop this from becoming real, and apparently it's starting to! With an asterix PBX as the hub, you could even easily spoof the number the call was coming from.

So someone in Russia can call in your absence. Technology is a wonderful thing.

Yes, reality often imitates art it seems. Remember Neal Stephenson's book "Snow Crash" written in the past century? Hiro was one of the original code inventors for Metaverse....and then there was Second Life;D