I have literally spent months on this forum as well as talking to several dealers about (1) how to get a Garmin hooked up correctly thru my 2011 SESG and (2) how to get the new I5 to work on my bike, as the Lightning to Pin adapter does not work with th iPod integration kit.
Well here it is...and it cost $20! Buy on eBay, Amazon, etc the EDUP EP-B3502 Bluetooth stereo receiver, and plug it in to your Aux jack (3.5mm) on the front of your radio. It is a fully self contained unit, smaller than a pill box. No wires hanging at all. Pair it with your iPhone 5 and bam...you're set. Play all of your iPod music right through your speakers.
Now, you ask about Nav? I have the FREE MapQuest app on my phone. I set my destination, Turn on the music and when the Nav app has a direction, it lowers the music and then raises it back after the verbal instruction.
As for power, the unit charges off of a USB cable so you can charge it on your computer or get a USB cigarette lighter charger and charge on the bike!
Gotta love America. I figure I just saved myself close to $1,000?