I would love to see an alternative to these services that could be self-hosted, but the reason why these services are useful for most people is because they have a simple web-based interface, even compared to something like Yahoo Pipes. This opens up their capabilities to non-technical users. If you’re asking people to edit configuration files, you’ve already lost them, unfortunately.
If someone can do that, that’s where the opportunity lies for an open-source alternative to Zapier or IFTTT.