When I still had the factory NAV I used the Peripheral iPod interface (PXDPGMT)...now discontinued.
http://www.crutchfield.com/p_541PXDP...ce.html?tp=120
I never had any real problem with it...no random light flashes or door chimes; it just worked as advertised. Peripheral changed their name to iSimple; they've got some new interfaces, maybe compare them against the ones you've already found.
http://www.pac-audio.com/productSear...&CategoryId=22