RoboFont is highly customizable by installing extensions. 

Available Extensions:

• Ramsay St.
• Shapes Tool
• Tiny DrawBot
• Type Cooker

Code is also available on git hub.

Third party extensions and scripts:

• Ted-Nudget by Jackson Cavanaugh 
• Interpolated Nudge by Travis Kochel
• hTools2 by Gustavo Ferreira 
  (read more hTools 2 alpha release)  
• Interpolated Nudge Dialog by Gustavo Ferreira
• Pangrammer Helper by Mark Simonson
• Assorted Python scripts for RoboFont by Dan Milne
• SidebearingEQ by Franz Heidl