Is it possible to set off a motion detector by shining something at it through a window

Question

or something of that nature (basically can I set off a motion detector in any way without even being inside the place where its at)

Answer 1

Yes.

There are a couple types of motion detectors...  

One uses microwave fields (supermarket door openers used to be like this) and they would trigger automotive radar detectors.  It was funny to watch cars slow down going by the grocery!

Another uses "passive infrared" technology where they detect changes in the infrared background.  

Then there are the toilet, washbasin, drinking fountain detectors that rely on changes to a reflected IR field.

All of these can work through most windows, although the last ones have pretty short ranges -- a few inches to a few feet -- 10 to 100 cm.

So some kinds of motion detectors watching through a window could be set off by your motion on the other side of the window.