Fool your friends, scare your cat, play a game while also admiring your physique! This "magic" mirror lets you do all that and more by letting you display words, pictures, videos, and even some games—all controllable through a mobile phone.
It works by rigging an LED matrix behind a two-way mirror.
The matrix is controlled by a IOIO microprocessor, and can be interacted with via an Android phone's Bluetooth.
Best of all, the creator documented the entire project, compiling a very handy tutorial on how you can build your own interactive mirror. It's currently just a prototype, but one can easily imagine potential implementations such a device might have.
If any clever WonderHowTo readers can come up with some cool uses for the idea, let us know!