Although esoTalk has little support for caching (nudging @tobscure here ;)), here's an actual (simple) cache implementation using a thin wrapper around APC as the backend.
The plugin in its entirety is available at https://gist.github.com/minecrafter/46673a1e4fefff622f6c . All you have to do is create a plugins/APCCache directory and drop the plugin.php in. It should been be able to be enabled and should work automagically.
Of course this is a plugin I made in a few minutes after reading the esoTalk source code, being bored, and wanting to improve the performance of our own esoTalk site , so I want some feedback and it obviously needs some work. But it is a good start.