Keychain sized simple circuit

I plan on making an Instructable about making a keychain sized simple circuit. I will be using the circuit board  shown below but I'm having inventors block. It should be able to take the stress of being jumbled up in a pocket. What should I put on it? If I use your idea I will mention and thank you in the Instructable. Thanks in advance.

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If you made a torch you could dip it in clear cast resin as a protective cover then add the switch.

A laser maybe? How about a blacklight LED and some invisible ink
pgd5000 (author)  killerjackalope7 years ago
Thanks I might do that, I was thinking about making a light but I hadn't thought about using resin.
jeff-o7 years ago
Once finished you could coat it in a few layers of epoxy.
How about using it for a small buzzer circuit w/ push button? It does require 8 button cell batteries, but it works! All you need is a 2N 2222A, a small capacitor, resistor, and piezo speaker. I can't recite the schematic right off the bat, but if your interested, just let me know! (just give me some time to get the schm. from my friend who built one)
seandogue7 years ago
A case. Ideally, a molded plastic case. Or you could just artistically wrap it with duct tape.