Relay modules from finder, custom pcb modules with current outputs for switching relays and optoisolators for voltage detecion, some custom expansion module for all signals interconnection. I will prepare some appendix to the blog-post with more technical data.

I'd love to see more details on that. The RPi is the easy choice for putting together a DIY system at home, but finding good and affordable remote I/O modules to run the show has not been that straightforward.