A Suretest is a handheld tester sold by Ideal that you usually see home inspectors using. Along with the usual ground/neutral checking it has a momentary voltage drop test using a 12a spike.
My concern with this type of thing as an inspector is you really need to know the load before you can compute voltage drop. I don't think it is reasonable to design every circuit for a 100% load at the farthest point.
