Product review (5 stars): Great Addition to the Tool Box
My electrician suggested that I purchase this to do a little legwork before he arrived.  I plugged it into the outlet, shut off a breaker in my unmarked breaker panel, and was able to glance to see if the little light was still on.  It did the trick.  I suppose using a little lamp would have also worked, but for ease and for future use, I'm glad I bought it.  It has other functions that will be important for future projects.