Hi everyone. It's really a good place, while other iphone developer forums are rejecting toolchain developers asking non-sdk related staff. I tried to post these, but crazy guys delete my threads every time. Then finally this forum, i got a place to ask.. 1. How to run apps in background without backgrounder, just like cycorder and dtunes. Backgrounder cannot run in 3.0 properly, but these two apps run quite well. I really wanna know how they did that? 2. How to detect the type of a function's argument? In the headers I dumped in iphone, a lot of apis take arguments of type "id". In objective-c runtime reference, there were some functions related(I think it is copyMethodArgumentTypePlease Register or Log in to view images, but I don't know how to use them. They always return "@". 3. How to create low resolution image from a high resolution image? I need to show a preview image. I really hope if someone can give me some answers or suggestions. Thank you.