If you want a hide-a-key option for your house, and you want something that will blend in well with your yard, weblog Factory Direct Craft has a simple solution. All you need is an old pill bottle.
Take your pill bottle and remove all the labelling. Then decide on what you want to disguise your bottle with. The blog suggests a pine cone, but a a rock might be a useful alternative. Then attach it to the bottom of the pill bottle with some sort of epoxy adhesive. You don't want to use hot glue or anything else that won't withstand the elements.
Once your spare key is inside, make sure you hide it somewhere that isn't near your door (where it would be easy to stumble upon). Once you've picked your spot, dig a small hole and bury it with the pine cone or rock on top. You're all set!
Pinecone Hide-a-Key [Factory Direct Craft]