Fur Sentry™

Have you heard of this marvel?  Seriously, every vermin-afflicted home should have one.
Here's the scenario:  I'm sitting on the couch.  Sometimes I'll hear the noise in the wall, and sometimes I won't.  But regardless of whether I do or not, the Fur Sentry™ does, and it comes galloping into the living room, fur rippling and whiskers streaming.  It leaps gallantly onto the couch-arm, and there it remains, motionless, until the noise goes away.  Which it always does.  Because ain't nothing getting past the Fur Sentry™.

By the way, I have no idea what's in these walls.  Bats (my guess), mice, muskrats, wildebeest . . . who knows.  I live in an apartment, so I'm not responsible.  My marvelous dad put screens in all my vents, so whatever it is can't get in that way, and I'm confident that the Fur Sentry™ will cover all other bases.