This seems like what you are looking for: http://math.typeit.org/
View the page source and it will hopefully give you some ideas of how to implement or what else to start researching.
Frage
I probably don't know how to search it, but is there a Ruby gem that would help users input math symbols by picking from a table?
Basically a gem that makes it easy to use symbols with a keyboard or touchscreen, and without drawing.
Lösung
This seems like what you are looking for: http://math.typeit.org/
View the page source and it will hopefully give you some ideas of how to implement or what else to start researching.