I have an ex-girlfriend that had issues with a stalkerish former boyfriend while her and I were dating. She lived in the lower level of a house, only one way in. Installed CCTV at the urging of her father and I. We put it up above the exterior light that was next to the door. At night it was about impossible to see (you'd be looking into the light) and during the day, well it was about as unobtrosive as it could be under an overhang, high and to the side. Just not something most people will look for or notice. There were a couple times it came in handy too, if nothing else as a deterrent (it was made known to the trouble maker that if he came over he wasn't allowed in, and anything he said or did would be recorded and used against him).