Directional

The people I know with answers won't give them when asked.  So I have a few Questions.

   There's several things to like about parametric (directional) speakers.  One is how you can aim one at any object and hear it's audio like that object is the speaker.

   The object could be a piece of furniture, an ash tray, even the ceiling.

   For the last 2 apartments I've rented there were times I could here sound above me.  It seemed to be originating from the ceiling.  Since that made no sense I had to mentally correct myself and assume it was the apartment above me instead.

   Now I know that my own phone (or anyone's phone) is capable of generating directional sound.  To have the ceiling become a speaker it just takes a cellphone in the right orientation.

   How would a cellphone know when it's pointed in the up direction?

   Because of the Accelerometer each one contains.

   That also means a cellphone can tell when it's in a pocket.

   It also means a cellphone can tell how far you've walked from your Vehicle.

   Those seem like unimportant details but they allow for tricks that could confuse anyone until they're backwards.

   But what would be the point of that?