There's no problem with asking the user about this; the point is not to do when the app is going into background. If you're concerned that most of your users w

There's no problem with asking the user about this; the point is not to do when the app is going into background. If you're concerned that most of your users won't want this, then turn it off by default and have an option to turn it on. The model to follow here is the iTunes Remote app. It allows you to remain connected in the background, but you have to activate it from settings, where there's a little explanation of the trade-off. Doing it the way this app does is plain nasty.