That is great. Yes, you can't project long on batteries, but that is not what is holding back implementation of projectors in handhelds.

The best thing about projectors is that they directly address the biggest (previously thought to be unavoidable) disadvantage handhelds have against laptops - small display. Laptops have battery issues too, all the time, because of the large LCD screen. But if you have a handheld with the option to dynamcially switch between a small display or a larger projected display, that helps to eliminate the display disadvantage of handhelds and in some ways makes the handheld preferable. Use a small screen when on batteries (laptops can't do that), and project when you can.

To summarize, it's not the batteries that is holding up projectors. If a projector could be put in a handheld inexpensively, and the only drawback was that it needed AC power, then someone would have done it.