An OSX tool for type designers for real-time legibility testing during design stage.
The font Wayfinding Sans Pro was made with this tool: http://www.myfonts.com/fonts/fdi/wayfinding-sans-pro/?refby=opentype
And since people ask about this all the time: This tool is not a standalone software I can share with you. It was specifically made to run with additional third-party tools and drivers on my computer. So if you are interested in using something like that, I can’t help you unfortunately.