Queue: Callback Caller

OK, so this has to be a topic that comes up all the time, but I haven’t seen hide nor hair of it here or on Google, so I am asking.

I want my callers, when things are busy and they have spent x minutes in the queue, to be able to press ‘1’ (or whatever), dial a callback number, and have the queue call them back so that they don’t lose their place in line.

Given all of the crunchy goodness that is available in FreePBX, I figured that this would be an option.

Have I overlooked an existing solution to this problem?