the reply to this helpful comment on this video has strong @cathoderaydude vibes and I can't explain why I think that.
as for the video subject, can't speak for the ruler but the volty (tiny leatherman bit driver compatible voltmeter) is a great product. required a small bit of filing to size but that was in the product description. Tiny, works on a keychain if you don't have a leatherman, as long as your key is conductive.
I can't believe they give it away for 4 [CoHost Plus! Equivalent Dollars (CHPED)]!