Just re-kindeling this one. Any chance that you could take a look at MLIrrigation and allow the generic irrigation module (or a new specific HAI module) the ability to send commands? If it was slightly modified to not require a serial port connection and just send commands, then the irrigation module could be integrated with HAI. Many use the outputs of HAI via connected relays to control irrigation.
While I can control the outputs via MLS, and integrate MLSchedule, and MLTImer along with scripting and so on, it would be nice to use the more advanced features of the irrigation package.