The GFCI outlet tester functionality works fine (you can buy those for less than $10) but the circuit breaker tracing function is completely unusable in my house. Once I plug in the sending unit to the target outlet, when I go back to my circuit panel and step through breakers following the directions, I will get positive notifications on about 4 of them and none of them are the correct circuit. The circuit that I did have it plugged into gave no indication at all.
I ended up having to have my wife call me on her cell phone while I individually cycled through every circuit in the house until we hit the right one. This tool was a big waste of time. I'm returning it.