I've searched, but some of the stuff said two years ago surely must be outdated. I want to just get in the car and listen to all 3 sources; broadcast, satellite, and internet/iPhone 4s. I don't want to plug in the phone. I gather that these are Under-$100 plug-n-play candidates:
http://store.griffintechnology.com/bluetrip-aux
http://www.newpotatotech.com/TUNELIN...link_auto.html

In addition, there are the over $250 + installation options, which have more features:
http://audiovox.diceelectronics.com/...ridge-info-avx
http://www.pac-audio.com/productSear...&CategoryId=55
(the "factory option" requires the phone to be plugged in, so it's less interesting to me)
http://www.g35parts.com/G35-iPod-Fac...999u7-ipod.htm

I ordered the BlueTrip, 2-day Amazon Prime, for a little under $59, but was wondering if there's a consensus streaming option for this particular car/phone combination?

I use the gogroove bluethooth adapter in my 06 sedan. One thing that I wish i had was bluetooth controls via the steering wheel controls. I drove a ford with sync recently and it was cool to hit next track and then pandora would go to the next track. I'm thinking about getting a better bluetooth adapter though so report how you like this one. The one I use you have to hold a button on it for 4 seconds everytime you start the engine to turn it back on. I just want to get in the car and have it sync up.