Koloroo have launched two widgets for the iPod, which, as far as I can see means it must be possible to run application software on it. If you can do that, then it is a platform, and then someone can do something really interesting with it from an audio / synthesis perspective.
An interesting interview with Chad Mealey from MiniMusic about the release of MixPad 1.0
I was looking at some of the other products from 4Pockets and found this.
Virtual Recorder is a personal voice recorder for your Pocket PC which works just like a good old fashion tape recorder. The program uses a ”true tape” mechanism which gives the ability to record over any portion of a previous recording, and is not limited to a simple append process.
One of the advanced features of Virtual Recorder is the ability to time stretch your recordings. This would allow you to listen to a full hours recording in as little as 30 minutes, without it sounding unnatural or like the recording had been speeded up.
This means that you can sample music and slow it down without affecting the pitch; allowing you to practice those difficult guitar solos or whatever!
The software also has a Cutting Room which allows you to splice recordings or remove unwanted sections. (Cut/Copy/Paste and Fade In/Out facilities are supported). Now that is quite advanced for a PDA application.