For people who care about the size of their waist line, this is a digital version of a waist line measure.
This is any regular belt of choice but with a buckle that helps in recording your waist line size. Outside appearances is like any regular belt and no one will notice any difference, unless you want to show it yourself.
Initially the digital meter displays complete length of the belt, say 32 inches. While we are wearing the belt we push the end of the belt underneath buckle over roller pin. As roller pin rolls, digital meter reduces the inches from the length and displays the result. Say 8 inches of the belt passed right under the buckle, then the digital meter shows the result as 24 inches. Your waist line measure is now 28 inches.
One advantage of this buckle is that you can place it on any belt of your choice. To make it more attractive, we can always provide the slots to replace the cover of the digital meter with different designs, so you are using the same digital meter for your recording of tummy size, but every time you wear a different belt to suit your dress. One more design change we can do is instead of digital meter being stuck to tummy and cover flipped out, we can flip out digital meter out so we can see the reading easily.