Scale

This uses JavaScript, so it doesn't need to be sneaky about being a scale. It works offline as well, if you add it to your home screen from Safari.

Unfortunately, I can't hide the Safari UI when opening it from the home screen because for some reason the Touch.force api isn't working if I do that.

Obviously, like all the other apps, you need something like a spoon to put your items on. Small fruit and vegetables can be placed directly on the screen.