We have a lot of fun with Halloween decorations, but every year lose a few to theft. Probably neighborhood kid pranks. This year I am considering to “tag” several of the more expensive decorations to set a notification alarm in the house and perhaps turn on outside lights if someone tries to steal them.
Example: Someone tries to steal an inflatable dragon 
, perhaps a zwave sensor registers that and notifies us.
Motion sensors do not work because many decorations move. Ideas?
I’d use a smartthings multi on the parts that don’t move, and when they do (acceleration) #evil grin# i’d turn on the sprinkler system 
Presence sensor would not work well since it only communicates with the hub every 30 seconds. That’s a long time when something leaves. Plus, I think there is a few minute delay after that before it is labeled as not present.
Personally, I like @sidjohn1’s sprinkler idea.
I like this idea! Now if I could just integrate my RachIO sprinkler 
Hmmm wonder if this would work with my new Spruce sprinkler system. 
I had kids kick mine but never stolen. Still. Spotlights, sirens and sprinklers would be a great deterrent.
The problem with using a multi sensor on inflatable items is the inflatable tends to be blown around by wind. Even the non moving parts register movement when the wind blows. (I tried this last year 
)
What about a pressure sensitive mat? This way if someone gets to close to the decoration, the pressure triggers an alert.
That can work as well
Mats are definitely good, but the trick is putting one exactly where the person will step on it.
You can also take the Indiana Jones approach and put the decorations on a mat and then trigger when the weight is removed rather than when it’s added. That’s a little more precise. 
A similar option is the one I use for my “hat trick”. Put the motion sensor facing up underneath the device so that it is blocked by the decoration itself. Then if the decoration is either picked up or knocked over, that should register as movement on the sensor. You might have to experiment with this one, though, to make sure that it won’t trigger just by the decoration moving around. That’s why for this particular option I prefer a PIR motion sensor rather than an accelerometer.
This isn’t going to work…
Where’s he going to get a huge bolder and hows he going to hide it so people don’t suspect a trap?
Boulder, CO… where else? 
You guys are so Evil! I Love it. You gave me a great Idea for the Halloween decoration and Scare the crap out of people.
Presto…I got a Scary Halloween prank!
For bonus points, load some sort of semi-permanent dye into the sprinkler heads. Then you’ll be able to tell who did it.
If, of course, you don’t already have them on camera…
What about some sort of laser “trip” system. That way if they walk up to the decorations they will walk through the laser and trigger the alert.