This may be a coincidence, but a man who matches your description was behaving in much the same way outside my house. This was yesterday at around 1pm.

I had just stepped off the bus and saw a man standing further up the road outside my gate. He was just staring at the house. Then looking up at the sky, then back to the house and through the windows. Not as if he were scoping the place, more like he was just staring really intensely. Very blatant, not trying to hide.

I hung back and observed this strange behaviour for about 5 minutes. He then slowly made his way up the road.

Slim guy, light black skin, slim with a slim face and a bit of a goatee.