If I get a phone with built in MP3 player (Motokrzr) can it be hooked into my Aux plug ('08 R56) to play through the standard audio system?

 

Yep. Just use a $5 male/male wire from the headphone jack on the phone to the Aux input on the Mini.

 

It'll work - just keep in mind that the cable you use needs to have a 1/8" jack (also frequently called a 3.5mm jack) on one end for the car's AUX input, and a smaller 2.5mm jack on the other end for the phone.

(Or, you can use an easier-to-find 1/8"-to-1/8" cord and just put a 2.5mm-to-3.5mm adapter on one end.)

 

Thanks guys, that's what I needed to know.

 

I forgot to mention: if your phone uses a 2.5mm headphone jack (most still do) you'd better make sure the adapter or cord that you use had the correct 2.5mm jack on the end, or try it out in the store before you buy it. If you don't get the right number of rings on the male end you won't get stereo sound from the phone.