Modify a toy helicopter into a very cheap drone that can be taken out of a pocket, thrown into the air, and then used to quickly map a building. Inspired by the elegant user experience of the manhacks of Half-Life 2 and the analogous economics of Chinese toy clones.
Some PCB with an ARM SoC and cell phone camera on it, machine learning, SLAM - I'm not really sure yet. It would be cool to use one of (the new <3 cm^3 laser pico projectors](http://www.st.com/web/catalog/mmc/FM132/SC1600/PF253322) STMicro is getting to market in order to do depth scanning, but the part isn't available to non-incorporated low-lifes like myself yet. Instead I might first try just a regular cell phone camera with a fish-eye lens saving video to flash memory. Then when the drones return to home base they can dump the video and image correlation algorithms on a laptop or phone can extract the 3D scenery. Another fun possibility would be to build some tiny galvos and add a laser. Then the camera on the drone could measure the offset of the laser dot to get noisy depth data. After collecting a bunch of that it would be dumped on home base for correlation and cleaning.