A while ago I bought a WW scale (the $40 digital version) and it works pretty well -- if I weigh myself 1st thing in the morning on weigh-in day, it usually matches with my weigh-in weight at noon.
Thing to remember with a scale -- it may seem like it's going haywire when really the problem is your weight can fluctuate up to 5 lbs in a day. That's why weighing yourself once a week at the same time works best to assess your weight loss. Otherwise you can go crazy watching the numbers!