Caroline is right - in BE you can 'wait on' someone, just by paying them a formal call. This is, however, very old-fashioned indeed, and I don't think I've heard it said 'for real' myself.
However, I too have heard 'waiting on' used where 'waiting for' would be more usual. Eg -
'What's the hold up?'
'We're waiting on one more person'.
'Does he know what career he's going to follow?'
'No, he's waiting on his results'.
The sense seems to be 'waiting for x before y can happen'.
I don't use it myself, as it seems to me 'waiting for' can do the job just as well, but I agree I've heard it, and I think it's increasingly common.
You don't give any context for where you've heard it, SwissPete. Was it something along those lines?
Louisa