You might want to know that iRiver is making Bluetooth headsets now. Granted, the don’t look anything special; does any headset? Also, the first model, the A100, is currently only set for release in China.
There’s very little to address here. It supports Bluetooth 2.0, which means that most any phone purchased in the last five years should work with it just fine. Yes, including that fancy, new iPhone 3G S.
What I will address, briefly, is: why isn’t iRiver more popular in the U.S.? (I can’t speak to what happens, say, in Russia or the UK.) Look at the LPlayer. Looks pretty slick to me; it plays MP3s. What more do you want in a player? My guess is that, somehow, we’ve gotten used to the idea that iPod/iPhone = MP3 Player, and anything else is pure garbage. It’s unfortunate, I think. There’s plenty of cool stuff out there that doesn’t have an Apple logo on it.