The built in mechanism to allow this to occur is the cron functionality.

What you want is currently not supported, but it is fully feasible to do, although if you want to allow execution of ANY !command it would be a mess.
If you want it to be limited to the script module, it's a bit easier, but it still requires interaction with cron

It's an interesting idea, and I'll need to think a bit about it, but I have a few ideas that might make such things even easier to do in the future.