As tracking devices, there is a lot of utility for Trackr Bravo, Iotera, and Tile. The distance between device and item makes a difference, so if you need one mostly for around the house, then Trackr Bravo is your solution. Otherwise, over longer distances, then Iotera is it.
Of course these devices can track not just things, but also people. By the same token, I imagine those people who track can themselves be tracked by other people. So, as it is with many inventions, I suppose, these devices can be used for good and not-so-good intentions.