If you've ever wanted to use your iPhone as a projector, but are too cheap to shell out for a pico-projector like the AAXA P1, perhaps this DIY system is for you. What you gain in price, you lose in flexibility, however; the system uses 35 individual laser pointers to recreate any bitmap font.
Video demo after the cut
The 35 laser modules are arrayed in a 5 x 7 matrix, slotted into basic PCB board. Each is wired up to a microcontroller - in this case a PIC16F722, though an Arduino would do nicely too - via five 8-bit latches. The software on the iPhone communicates via the serial port, and lets you type in a sentence and have it automatically mapped into different laser layouts.
One suggestion is to swap the cheap lasers - which cost $0.40 each on eBay - for something more powerful, and use the iPhone as a portable projector to paint slogans on buildings. Not much use for enjoying impromptu mini-cinema-style movies, but a cool hack all the same.