After a quick google search found this http://www.energyvanguard.com/blog/59782/A-Great-Tool-for-Checking-Insulation-in-Walls
Won’t tell you how good the insulation is just whether it’s there or not.
P.S.- to flu’s point yes, I have one of those, mine has a somewhat big head, doesn’t always fit into holes. I was thinking more of a device like a stud finder would be cool.
