OpenSprinkler is currently designed to work with 24V AC valves only. It’s probably quite difficult to power these valves with battery / solar panel. Technically you need an inverter that converts DC to AC, but I’ve seen discussions that these AC valves can run on DC voltage (al beit less efficient / draws more energy than running on AC).
We have an upcoming product, OpenSprinkler Bee (http://rayshobby.net/cart/osbee-10) designed to be battery powered and work with latching solenoids. The controller will have an RF transceiver which can remotely talk to a main controller that has Ethernet connection. It’s probably also possible to add a bluetooth module to allow phones to directly talk to it. I keep telling people that I am working on it but the truth is that I haven’t made much progress yet 🙁