Its still early in development, but I'm working on a Python library that knows how to call the OpenLP API, and I'm working on hooking it up with an OSC frontend so that I can control OpenLP with TouchOSC. The library I'm working on could probably be used with WebDings if you prefer to use Midi.
The repo is here on GitHub: https://github.com/rickprice/openlp-OSC-control
Comments welcome, etc.
The Web API of OpenLP so far is quite straightforward to use with Python.
Frederick