David:
I have completed a semi-related project using a Raspberry Pi running this GitHub repo:
https://github.com/nfarina/homebridge
Using the Homebridge-CMD plugin:
https://github.com/senyoltw/homebridge-cmd
Basically, it takes in a Siri (Homekit) input, and outputs any cmd command line you set up.
I’m new to OpenSprinkler, but if OpenSprinkler allows any sort of command line operation, then it should work.
For example, if you can do something like the following at the command prompt:
opensprinkler:~ root$ opensprinkler-run zone1 now
… then it should be possible to get this working.
Have a look at homebridge, it’s a pretty fun project in general, and it most likely can be used together with OpenSprinkler.