We were getting stuff done this weekend, and as is her style, the wife made a list of what we wanted to accomplish. One item was the changing of smoke and carbon monoxide detector batteries (we'll ignore temporarily that this is the weekend DST had been happening for the last 20 years, and as such we would normally have done it now instead of three weeks ago; I assure you that is just coincidence.) She had written the note "change smoke and CO detector batteries" as someone who is a geek would do (she'll also do things like "δ oil"). Thing was, when she went back to it she read CO as Colorado, thus, "Colorado detector".
Here's the thing: If I had a Bluetooth GPS and some programming chops, I could make a Colorado Detector. It just takes 4 coordinates, and if you're inside them, Colorado, if not, not. I think this would be enormously funny. One could also program it for Wyoming and Utah. You can even get chipsets and do some device hacking, and then have an indicator light or small display in a handheld unit.