Wireless sensors that can attach to your keychain or other items so you can track them down when they're lost have been around for a while. Two companies have captured most of the attention: Tile and TrackR. On the surface, they both appear to be very similar, but if you're looking for that little extra, I'd checkout TrackR over Tile. TrackR's sensors are thinner, do more and don't use special batteries, so you can replace them yourself. One of the coolest features of the TrackR sensors is that you can use the sensor on your keys to figure out where your phone is when you can't find it too. They all use higher powered Bluetooth, which has a range of 100-150 feet of bidirectional communication. If you buy them in volume, they can be as cheap as $15 each, so you can use them in your wallet, travel bags or anything you'll ever want to track. I've posted the link to TrackR at DataDoctors.com/radio https://www.thetrackr.com