There are about a dozen different IR repeaters and systems available for iPhone out there. The problem is that they aren't Logitech easy, and most are pretty silly. That is, when you get the really small buttons, it's not always easy to use as a remote, and then you still have to properly program all the logic behind it to make it work.
That said, I use mine within a Crestron environment, and I get full control of my 14 zone system from my iPod within my home with no problem. It shows me what is playing where, and then gives me remote control of the current device in the room with two way feedback, like the current XM station and song playing, or lets me know if the TV is on in the kids playroom.
It's all IP based, so as long as I'm at home under our wi-fi umbrella, I have control. Still, I much prefer my (Crestron) hard button remotes over the iPod for control any day of the week.