Excellent thanks, this is what I was looking for.

One last question if you don't mind; is there anyway to pull the caller 
out of a fifo after a certain time either from api or by setting a 
variable (eg. the destination didn't answer after sometime, so carry on 
in the dialplan to eg. voicemail)?
  
There is a "uuid_transfer" that will allow you to route them accordingly.
Regards,
Chris