The Stalwart Hide a Key Set looks so much like the real thing. Only you will know where are your keys.
The Thermometer really works and hides the key, how cool is that. This device is an awesome imitation of the real thermometer.
The Rock is a good looking rock. If you put it with a bunch of other rocks, I am quite certain nobody would notice any difference or suspect anything.
The Sprinkler is a great idea too. You could probably fit 5 keys into this if you wanted to. I am very comfortable that this unit is buried in a spot where it will get very wet, but my keys are safe from the elements.