If you can dream it, Arduino can help you build it -- perhaps with a dash of MakerBot thrown in for good measure. The latest homebrew project to hit the ol' inbox sounds an alarm whenever you leave a room without a registered item. Doh (named in Homer Simpson's honor, we presume), uses a trio of devices to track items that you usually travel with, like your keys or a cellphone. After you've assembled the rather complex contraption, you affix color-coded RFID tags to your gadgets, before registering them with the Arduino-based host. If you leave the room without all of the items that you've registered as
