I use this and highly recommend it: http://us.kensington.com/html/17812.html

It uses acoustical labyrinth principles to amplify - needs no batteries or other power source. 

I, too, use a nav app, and I can tell you that it makes the sound coming out of my iPhone's speaker at least twice as loud - just what's needed for our less-than-quiet Vanagons. 

I paid about $30 for it, online. 

David in OK

Sent from my iPhone

Begin forwarded message:

> From: Gregg Carlen <gregg.carlen@GMAIL.COM>
> Date: February 6, 2011 1:46:36 PM CST
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Vanagon iPhone dock ideas
> Reply-To: Gregg Carlen <gregg.carlen@GMAIL.COM>
> 

> If you figure one out, let me know. My new (to me) van arrives on Tuesday,
> so I'm going to have to figure out how to mount my phone in the van, too.
> I've a GPS app, so someplace visible near the driving line of sight is going
> to be a must.
> 
> A friend referred me to this site below. Seems like they have just about
> everything in terms of mounts.
> 
> http://www.ram-mount.com/
> 
> Gregg
> 90 Westy (will trade you a hamburger today for a Vanagon on Tuesday).
> 
> On Sun, Feb 6, 2011 at 1:08 PM, Zeitgeist <gruengeist@gmail.com> wrote:
> 
>> Any ideas or examples that work for the Vanagons?
>> Casey
>>