i have the belkin Tunebase with my iphone and it works really well with the Tuner app. There is a slight interference through the speakers but im not sure if thats the fm transmitter or the 3G signal interference.
any fm transmitter will tranmist whatever sound your iphone would put through your iphone's speakers will come through the fm transmitter, which includes streaming music and phone calls.. atleast that is what i was told.
Yes. I've done it before. The only problem with it is the Interference that EDGE creates that causes the buzz in speakers nearby. In my car I can reduce it by putting pressure on the connection, but you can simply run your speaker cables through a magnetic doughnut (like on USB cables) to reduce the interference.
Also bear in mind that the play/pause control may not work as expected. I've had a case where pressing a remote [PLAY/PAUSE] button while streaming in Safari didn't actually stop the stream. Instead, it started the iPod application playing (which did - in fact - stop the stream - but only incidentally).