I used to keep my keys on a standard carabiner, which I could clip to my belt loop. Most of the time, that worked fine. But every so often, when I unclipped the carabiner from my belt loop, one of the key rings would slip off without me noticing. I had spare keys, so such events were really just a minor nuisance. Then, I got a car with an (exorbitantly priced) keyless entry remote.
One day the inevitable happened, I reached for my keys and the ring with the remote was gone. Staving off the panic, I assured myself that it would turn up. Luckily, the lawn service at my apartment came across it a couple days later... after they ran it over with a riding lawnmower.
Staring at the mangled corpse of my absurdly costly key fob, I resolved to solve my key loss problem once and for all. With the simple hack I describe here, I haven't lost a key since! (Though I have yet to replace the remote.)
This project was made proudly at the i3 Detroit