iTunes Radio was one of the big feature of iOS 7 at WWDC which allows users to stream music and it is integrated in to the mobile operating system. When iOS 7 is launched in the fall iTunes Radio will only be available in the U.S. at launch, this is because Apple has to set up licensing agreements with each label in each country before they are allowed to launch iTunes Radio in that country.
The developer version of iOS 7 still allows the developers to use iTunes Radio and fiddle around with different things but that is because it is not ready for public use yet. There was a mention at WWDC that more countries will be added over time but there is no news when specific countries will get the service. This is the only feature in iOS 7 that you will have to wait for the rest of them will be ready to use at launch in every country, there has been no specific date set for the launch of the software it is just said to be launch in the fall.
The iTunes Radio service will be a massive competitor in the streaming business because all iPhone users will have access to it on their phones within seconds.