EDIT It seems I was mistaken in my previous answer because the device did not launch the released version of iOS 4.3.
There is a way to provide an AirPlay button on the user interface.
Use MPVolumeView and add it to your view hierarchy
MPVolumeView *myVolumeView = [[MPVolumeView alloc] initWithFrame: overlayView.bounds]; [overlayView addSubview: myVolumeView]; [myVolumeView release];
MPVolumeView provides a volume slider and a route button (see image below). But I do not think that only a button can be displayed.

Jilouc
source share