This is embarrassing, but it is what it is. I placed a SmartSense Multi Sensor somewhere in the house over a year ago to monitor temps and thus turn-off an evaporative cooler when the house was cool enough. Now here it is a year or more later and the battery is getting low. My wife frequently babysits the grand kids, so I put it somewhere they wouldn’t mess with it. Unfortunately, neither my wife nor I can remember where it was that I placed it. We’ve hunted all the likely locations, but without any success. Any suggestions on how to track it down using technology? I’ve thought about using a space heater to heat specific rooms to narrow the search, but since it only reports temp every so often, it means leaving a heater running potentially running a long time, and then having to re-cool the room once that room has been crossed off the list of potential locations. Thoughts?
Since it can also measure vibration, set up a notification for vibration, go room to room and knock on each wall. You should have a good chance of zeroing in on it.
If you don’t find it the first time around, you can go around again checking smaller sections.
You can also use a broomstick to knock on the ceiling. And if you think you might have put it in a drawer, include knocking on countertops and desks.
Sometimes in situations like this, it was mounted, but came loose from the mounting and fell down, meaning it may be behind a piece of furniture or even stuck on a curtain rod.
Note: “acceleration” is the same as vibration in this context, so you can use the “Notify me when” app under Smart Setup for this purpose.
Number 21 under Convenience
Good one JD. Simple solutions are always the best. Since it’s zigbee I was about to suggest moving the hub around the house with a long patch cable, checking the signal strength. Tapping works too. 
Thanks. Moving the hub around would be worth a try for something like an open close sensor that doesn’t detect vibration. You might at least be able to figure out what floor it was on. But it would be difficult. The problem with signal strength with a zigbee device is that Signal strength is so low to begin, and gets thrown off by all kinds of local materials, so it can be really hard to find a device on that basis unless you’re using pretty sophisticated equipment.
And on top of that it’s a sleepy device, which may be asleep when you walk by with the signal detector. Another advantage of tapping for a device without acceleration sensor is that it should wake up the device. 
Thank you for the suggestions. I tracked it down. Discovered it underneath a dresser it had been mounted behind.
Glad to hear it! Adhesives do lose strength over time, so that kind of thing can happen.
So did you find it just by looking for it visually, or did you use vibration detection?