I would check into the average frozen depth of your local lakes in the area. A meter sounds good until you come to find that a yard is the average frozen depth for your area lakes in winter.
I would just contact my local DEC, and ask them about the average frozen depth of lakes in and around your area. If they don't have this info they should be able to tell you who does. Actually now that I am thinking of it your local Sporting Goods Store should know the answer to these questions. Because they know when it's safe for Fisherman to drive there vehicles on the lake. I've seen people drive Hummers and Yukons out to the middle of a lake. You gotta have BALLZ of steal to do something like that - Really!