I recently bought a new car stereo. In an effort to retain the steering wheel controls, without resorting to an aftermarket adapter that is a bitch to install, difficult to program, and doesn't work very well even when you've done both correctly, I came across an adapter made in the EU by the company that makes my radio. It's odd and frustrating that such an OEM adapter doesn't exist in the USA, but that's not the most incomprehensible thing I've come across in my search.
This is. (warning: pdf)
I've studied these instructions carefully, and have found little clarity with repeat visits. Each picture seems to bear no relationship to the others, and the lettering scheme is impossibly confused. The Dutch, without the benefit of the English language,
seem to have done better (another pdf).
I have little doubt that I could figure out how to install this thing without instructions if I found it cheaply enough to purchase (unlikely, given the exchange rate), but the "official" instructions certainly gave me a chuckle.