This is an instructable for a cheap auditory disc golf disc locator using a key finder! I'll show you my idea and procedure, but it could certainly use some improvement. Be creative and make it more robust it if you like the idea.
The obvious one is the disc golf disc, but the crux of this project is a wireless key finder. You can pick them up at your local hardware store and every one that I saw was under 10$. I bought a less expensive one but I'm sure the more expensive ones are louder and have a longer range which would be nice.