fyi: I’m working on an openHAB2 binding for the Rachio controllers (I fact it’s already in beta state).
openHAB Version 22 is a powerful open source home automation system supporting a wide variety of devices and provides powerful automation options. Using HABpanel you could easily run it on any type of device using the browser.
The binding integrates Generation 2 controllers using the Rachio Cloud API. All controllers / zones will be auto-detected once connected to the cloud service (in theory an unlimited number of controllers and zones as well as multiple accounts). You get status information and could start/stop zones. Based on OH rules you could create your own schedule logic. It also integrates the event API, so you get notifications when watering starts, info on run-times etc. Gen 1 might also work, but I have no device to verify (depends on API support).
Let me know if you are interested to give it a try. I will become available on the Eclipse IoT market soon. Check the openHAB community for more details.