This could be extraordinarily useful to graphic designers (especially UI folks) with the incorporation of typography and resolution converters. E.g:
• Pixels (px) at Resolution (ppi) = Length (millimetres, inches, …), and inverse
• Points (pt) to Length (millimetres, inches, …), and inverse
• Ems (em) or Ens (en) at Point Size (pt) and at Resolution (ppi) = Pixels (px)
• (et cetera…)
It used to be that 1 point was equal to 1 pixel, but with mobile and "retina" resolutions there's no longer any consistency.