Mint Wireless Limited loaned me one of their Aiptek Pocket Cinema V10 projectors to try. This is a unit about the size and shape of a mobile phone and projects an image of up to 1.27m. It will play videos and audio as well as show still images at 640 x 480 Pixel VGA resolution. It has a built in battery and charges from a USB cable as well as mains adaptor. You can also play composite video and stereo audio.
However, the unit has several limitations. The unit does not appear to be able to display the live image from a computer screen: there is no VGA connector and the USB link only works to transfer files for later display. The screen is not very bright and so needs to be used in a dim room. The sound quality from the tiny internal speakers is poor. The price is under $AU700.
DELL offer the much larger (but still small), Dell M109S On-the-Go Projector for $US499. This has 858 x 600 SVGA resolution and VGA input. It appears to lack the speakers, battery and internal storage features making it dependent on external devices, whereas the Aiptek Pocket Cinema can be used on its own.
Like the Apitek, the Dell uses a LED light source in place of a conventional light bulb, making it more efficient and longer lasting. The Dell uses more power and therefore hopefully is brighter. The Dell unit looks better for use with a PC for presentations, whereas the Apitek may be useful where you just want to play a video or an audio slide show.