A recent patent application from Apple has been spotted that outlines a process for handheld devices, like the iPhone and the iPod touch, to stream music online. More specifically, in Apple's case, to stream from iTunes. Apparently a simple directory of all owned content can be hosted on the device, and then streamed on-demand, provided the device has access to the Internet.
It gets more interesting in that a device with cellular wireless connectivity, like the iPhone, could potentially stream all the time. Certainly an interesting concept though Apple is known for filing numerous patents that many times we don't hear about for years, but this certainly seems like a prime time to offer such a service. Cell companies likely wouldn't be happy with millions of connections streaming at once, but it is pure novelty to think of streaming your entire mp3 collection to your phone.