The iPhone 4 is a great smartphone and now, you can use it as a projector, thanks to the Sanwa Pico projector. Called the Sanwa 400-PRJ011, it is compatible with both iPhone 4 and 4s and has a built in 2100mAh battery to make sure it does not sucks up the valuable battery juice from your iPhone. Check out this Acer projector released in 2013.
The projector doubles up as an external charger for the iPhone too. The projector can output 640 x 360 pixel resolution and has 1000:1 contrast ratio. It can project up to 65 inches and retails for 260 dollars.