I have several of them plced in various areas.

Cons: (which can be compensated for) --If facing sunlight or an area where heat inversions are likely, it will give false alarms. ----Birds, other animals,insects moving leaves/branches/grass can give false alarms. Oh yeah, when the batteries get low, especially in freezing weather, you'll get false alarms.

What I did was to take black electrical tape and put strips over the sensor leaving a 1 inch slit in the center of the sensor. It narrowed the field and a larger object such as a car, person, deer, Yetti will set it off. Then I inserted them into small bird houses where the sensor has a view of the opening. This practically eliminated the sun and heat inversions from setting it off. I had one of these sitting on the porch too so if the cat showed up, I could let it in.

In general, I am happy with them. I bought them at Harbor Freight for about 20 bucks each.

I plan on trying those garage sensors. When anything breaks the beam, a relay will set off a chime. The Driveway Patrols have been doing the job so I haven't taken the time to play with the idea. You can also get (or make)one of those pressure sensitive mats and put them by your doors. I have a friend who put one of those air hose things gas stations used to have that dings when someone rides over it, across his driveway.