Everyone,
I spent a little time this weekend writing myself a twitter plugin for Indigo with support for direct messaging to/from Indigo. It's not the simplest setup as you need to create a twitter application but there is little I can do to avoid this. By creating triggers you can action and respond to messages from yourself (or another user).
The code can be found at: https://github.com/KieranBroadfoot/Twitter.indigoPlugin and I would advise reading the readme before getting started.
One word of warning. The plugin utilises two separate subcomponents to send/recv with twitter which run the system default python and the IPC needs improvements.
Good luck, and hope it helps someone.
k.