I've been searching some of the other forums, and it seems like you can get bluetooth functionality on the older X3s (I've got an '04 with assist), by replacing the existing TCU with the latest model (Part # 84109195455). It seems that you may need to recode your car at the dealer, but since the TCU retails for around $350, it is still a lot cheaper than buying the $700 ULF (which also kills your assist).

Has anyone tried this?