My guys have this:
They usually will watch that while they're getting their diapers changed. They also have the TinyLove Take Along Mobile that's hooked to their cribs. That thing runs for 30 minutes and just sips batteries... they last forever. And its not a huge investment, so I'm not heartbroken that they'll only be using it for another month or so. The sound machine/projector will have a longer life as long as they quit throwing it off the dresser.