I needed to serve some WordPress posts as web views to some mobile apps. But the app guys wanted the all the images inside the_content to be encoded into base64-strings, for offline caching. This was made into a tiny little plugin which you can download and use as you see fit.
When enabled, this plugin will encode all images sitewide on your website. This is generally a bad idea. Should you need help tweaking the plugin further, just drop me an email.
Download the plugin here.
UPDATE: This plugin is now released at the WordPress Plugin Directory. Download the plugin here.