J2ME is probably not a good choice for audio streaming. I suppose it's possible since MIDlets can be multithreaded and some devices have multimedia capabilities but this is still rare.
What device/carrier are you working with or can you pick one?
You certainly can't do this with a stock MIDP 1.0 device. There is no support for playing digitized audio.
Some MIDP 2.0 devices could play audio files and some 1.0 devices have carrier specific API extensions to allow audio playback, but I still don't think any of them could stream audio playback. I honestly don't know. Spend some time reviewing the 2.0 specs.
If you can use a Palm device then I'd write a native Palm application rather than a MIDlet. In fact, I believe the Treo 650 comes with RealPlayer that will stream audio playback right out of the box. Certainly PocketPC devices with Windows Media Player can do it.
William Frantz
http://sprintdevelopers.com