Like any good project, this one started with a problem: how do I let my wife know I'm in a meeting so she doesn't let the dog barge in? (I work remotely and my office is the only way to get to the backyard.)

The solution: build my own "On Air" light that turns on/off automatically when I'm in a meeting! Sure, there are commercially-available products that do exactly this, but where's the fun in buying something when I have the skills and equipment to build my own? Just how hard could it be? (famous last words)