Well my last truck didn't have an aux jack, but now my new truck has both, bluetooth and an aux jack. In this case the bluetooth is much better as I can use the controls on the steering wheel to make and end calls without touching the phone. HOWEVER, my Goldwing has an aux jack and I've been trying to not buy bluetooth for the helmet (very costly) and it looks like this great tip will now solve my problem with the phone on the bike. I've not tried it, but it sounds like it will work.
I say all of this just to point out that one, THIS WAS A GREAT TIP, even if we should have all known about it, and two, thanks for posting it and not thinking that everyone knew about it. Sometimes we can't see the forest because there's too many trees in the way. :-)