I've been wanting to try a FISCON unit.
Seems to offer the most OEM compatible solution on the market - RNS-D, RNS-E, non-MMI radio (such as Concert and Symphony) specific models, as well as the modern stuff.
A2DP audio streaming, complex phone integration etc.
They don't specifically say they're A/S8 compatible. They do specify A6 (4B (C5?)) and A4 (B6).
However I would have thought that an RNS-D is an RNS-D (or a Symphony a Symphony for that matter), so don't see why it wouldn't work in a D2 (or a B5!)...
Expensive units though:
€226 excl tax.
€269 within EU.
Links:
RNS-D.
Audi other (non MMI)
Related product to improve RNS-D multimedia integration
here