I know that the 3.5mm jack in the rear is really an AV minijack; however, has anyone here ever used a standard audio mini-jack in the rear and use the AUX source as an audio-only AUX-in?

The part that Pioneer recommends in the owner's manual for the AVIC NEX units (CD-RM10) doesn't even seem to be even sold by Pioneer anymore.

 

I've not done it, but I don't see any reason why it wouldn't work... you just won't get any video. 

you can get the cd-rm10 on amazon, and use only the audio leads, sells for 8.99, free 2 day delivery with prime.