There's a reason why the Japanese aren't nearly as fat as Americans. Tanita's BC-502 scale can measure your weight and send a small current through your body to tell you your BMI and fat ratio.
What makes this unit special is that it can be connected to a PC using a USB cable so you can chart your progress in losing or gaining weight. Not only that, they have a bluetooth module that can sync up with your phone, so you won't have to bend down to read the scale (and for keeping track of your progress).
Once on the phone, the data can be sent to a website so your doctor can monitor your health. Maybe now we nerds will be tempted to get back in shape? Nah.
Tanita BC-502. the geek's Bluetooth scale [Akihabara News]