I know that you need a Mac and Xcode and the SDK. But is it possible to develop apps for jaibroken devices and/or regular devices using Windows/Linux platforms ?
Also, what's the lowdown on the Airplay SDK ? Heard that it's pretty good but doesnt offer the same performance as an app developed through Xcode. Found this PDF Document, for what it's
Short answer -- YES.
Although i'm not entirely sure what you mean by "ONLY" for jailbroken devices, but if you have any experience at all with flash scripts or action scripts then check out Adobe Flash Professional CS5.5. It's a program that lets you design and write your own apps for ipod/iphone/ipad.
http://www.adobe.com/products/flash.html
I've used it for years and find it perfect.