Ive tried for 3 days now for them actually do tell me my weight. You have to bang them on the floor to get them to start then they flash '0' for about 10 times then switch off.
I have these ones too. They do work and I find the body fat/bone density function interesting however, they do weigh me 1 and 1/4 pounds heavier than the scales in my WW group!
I got these ones last week and so far so good. Only thing is they were bigger than I expected but they work perfectly. And I find even if you move it the weight doesn't change like most other scales.