That's a good idea, and there is precedent for it working. Pastebot wouldn't ordinarily be allowed to run in the background, as it isn't one of the predefined

That's a good idea, and there is precedent for it working. Pastebot wouldn't ordinarily be allowed to run in the background, as it isn't one of the predefined types of background app. They decided to configure their app as a media player and play a silent audio file when they wanted to run in the background. Apple wouldn't allow this, but as long as they play audible music - so they are actually a media player - it is permissible. You'd have to go to the trouble of building the functionality and submitting it to Apple to find out though, and you'd be running the risk of Apple changing their mind at any time.