My husband got this little gizmo as a gift for Christmas one year. And I have to say it has definately come in handy.
The tool is about six inches long and about 2 inches wide. It fits perfectly in my hand. But, what I like the best is the EASE of use! Really, this tool is so simple, I routinely have to take it away from my 8 year old because he likes to "play" with it.
You simply put the unit against the wall and push the button located on the side and slowly sweep it across the wall until it beeps and the red light comes on. And for those of you who have impaired memory (like me), these directions are printed right on the back of the device.
When we moved into our new house, I used this to help me hang the coat rack and heavy pictures so that they are nails are in WOOD and not just the dry wall.