Fast foward to 13:27 of the video to see it in action.
Mojoptix has developed an Open Source digital sundial that you can download and make if you have a 3d printer.
The sundial has a few caveats like it can only tell time between 10AM and 4PM and also only in 20 minute increments. So for example, you will only see time like 10:00, 10:20, 10:40 rather than numerals between :00 and :20. This is understandable considering the dial is still limited to shadow play and works with very sensitive angles to display these times in analog.
You can find the Openscad script and the STL files here: