Hidden Jewelry Holder - This is an awesome DIY project. All you need is a couple nails, some hinges a little bit of altering and a place to hang a pretty picture. I think it's a good idea, and a convenient way to hide your valuables.
I love things that hide things. I especially want that bathtub and the vent/safe. The TV hiding all the other electronics is a great idea, but I'd imagine there'd have to be some kind of sensor in order to work the other stuff.
Free DIY Project Plan: Learn How to Build a Jewelry Organizer. I know this is how to build something for jewelry, but wouldn't it be awesome to build it and modify the front to hold pictures and the inside for art stuff?