Key finders

They only work if they are attached to the keys. And most of the ones out there are limited in that you need to know where the caller unit is to find the keys.
I cannot help with the first issue, mine were hanging together on the key rack for nearly a year before I put them with the keys. The second issue is covered with these:

Not your ordinary key finders here, nopity nope. first thing you will notice is a warning that they are loud. They easily double as a panic screamer, it is part of how they work. Secondly, they call each other or can be called with a sound produced from your phone or computer through their web site. Granted, the range isn't the same, as your phone doesn't have the volume necessary to call the finder at 100 yards, claimed ideal condition range. So, in effect, you are getting 2 finders in one order. If you cannot find either one, use your phone to scream for them.
The XL in their name means Extra Loud, they weren't kidding. There is also a light that will blink when the finder is sounding its alarm.
Through the web page interface, you can also set the finder volume and assign them to a channel. The channel function can be useful to choose which ones respond to which paging tone.
They are encased in a no nonsense poly-carbonate shell that can withstand anything you can throw it at. Batteries are user replaceable and last about 18 months per the company web site.