The units of physical quantities are extremely important to scientists and engineers. They communicate a lot but, unfortunately, can lead to huge and costly mistakes. An add-in has been developed to help manage units within JMP and reduce these errors. This add-in uses the new JMP 18 Python integration to easily do what would have been difficult to achieve in JMP 17. This presentation shows the capabilities of this add-in, as well as how it was developed, including Python use, source control, testing, documentation, and build systems.