Instead of me manually entering my weight & body fat, how about having some integration with the Withings wifi scale?
Here's the API link
http://www.withings.com/en/api/bodyscale
Sure it's possible to use MyFitnessPal as an integration bridge but that extra complexity shouldn't be necessary.
I went looking for something like this recently & came across this fantastic project on github - github.com/.../
Needs a Linux system or VM. Luckily my desktop PC at work runs Linux so it syncs the reading from the scale for me once every night.