last year i made one out of an old samsung cellphone charger, but few emulators and games worked fine, and its really unconfortable if you use the caanoo its better to use a joypad. but you depend on the caanoo's battery. it better to buy an old notebook with tv out( i use the motherboard of an old compaq cq50 inside of a old dvd player. they run smoother and fast. also battery is no a limitating issue.
and of course you can emulate and play tons of different systems...
hope this was helpful