Ah yes, modern technology...
I once borrowed an empty CCTV camera housing from work. I couldn't borrow a camera - FAR too expensive back then.
I mounted it on a block of wood made from some 2x4 offcuts, ran a short length of twin-ax from the back to an old 1200 baud modem and left it pointing at the inside of the door to the flat.
The woman from the letting agency thought it was some sort of weapon and called the police...
On the bright side, the letting agency didn't hesitant to sack her when confronted. Naturally they claimed to have 'no knowledge of her actions'.