We use Frontapp system to manage our emails and they provide a way to build plugins for their app. http://dev.frontapp.com/plugin.html#creating-a-plugin
From their site:
You can use any web framework or library you wish: it’s just a web page that can communicate with Front. It has to be hosted on your servers and include our library. Just add:
Does anyone know if it would be possible to do something like this (create the plugin) with bubble?