I have a Tanita scale that measures body fat. Unfortunately, the instructions say it is not reliable for body fat first thing in the morning (something about hydration levels). And I don't like to weigh myself other than first thing.
I think they recommend weighing yourself at the same general time every day but NOT first thing in the morning. Like before lunch or something? Which can be hard to do.
I've also heard many times that these home body-fat measurements are inaccurate, but it could at least help you track a trend even if the number isn't exact. However, because it is subject to hydration, retaining water will mess with your number (just like it does with the regular ol' scale -- darn!).
All that said, when I had my body fat measured at the gym with the calipers pinching my thigh, my arm and my midsection, that measurement did match my scale exactly (when I dared step on it in the middle of the day).