Instead of telling my weight, they'd tell me I weighed the same as Paris Hilton--oh, wait. That was just my right leg. Oops--Mr. Ed. I weigh the same as Mr. Ed!
I haven't tried them, really. But it seems that's about how they'd work. And I have to wonder which would be the greater impetus to stick with my eating plan: seeing what I really weigh (eek!) or being told I weigh the same as a talking horse (double eek!).