Do U know of a background auto shut-off app?

[Boccaccio70]

I would love to use my iPad as a music dream machine, and play Pandora et al with an utility app that shuts the
iPad off after a user selected time, so I can fall asleep to it? Has anyone out there found or know of an app that
Can do this and piggybacks on Pandora or run in BG? Thanks-Mark