I'd like to build an app that does measurement conversions for those who often find themsleves stuck between the metric/imperial system gap.
As a product designer working in America but producing things overseas, I often have to work keeping both measurement systems in my mind at the same time. Clients want to know the dimensions of objects in inches, but production drawings and info often need to be specified in metric. It's usually a two step process to get the dimension first from metric to imperial and then from a imperial decimal equivalent to an easier to understand fraction.
My app will do the basic conversion from metric to imperial units and will have additional functions that convert the imperial decimal equivalent to a useable fraction. The decimal to fraction calculator can include options to round up or down to the nearest quarter, eighth, sixteenth, etc. depending on your needs.