I'm a long-time Slingbox user from ipad and iphone. Ipad still works perfectly. Iphone recently stopped working UNLESS I've first powered up the slingbox using the Ipad.
My iphone shows Guide and Gallery and a START WATCHING button, but won't show the remote. It expects you to rotate the iphone to make the remote visible. Since the latest IOS update, the iphone screen won't rotate on the Sling app until after the Slingbox is powered up. After that, all works well, the remote shows and the phone does things perfectly.
By the way, YES, the rotate feature is enabled on my iphone and works in all other apps.