I have stumbled across this thread when i was looking up some info on the power folding facelift mirrors.
its basically a LED light that is fitted onto the under side of the wing mirror and it comes on with the ch/lh feature.
now it seems that it only works with the MY09 mirrors as the new MY11 mirrors never released the correct trim to get it all working, but as far as i know the MY09 mirrors were the same across the range so the trim should fit onto our A3s that have these dumbo's.
it looks pretty cool and from the prices mentioned on that thread it looks to be really cheap to do. just a fair bit of wiring and messing around.