I've been looking for compatible irrigation controllers as well, and this looks like a great device. I wonder if it would be possible for Securifi to create a single UI type that can contain a variable number of relays (switches). This controller could present as one device, with 15 different toggles in the device's UI item.
I've also run across a pool filter controller by Intermatic (couldn't find the link) that has 3 Z-Wave relays; it could use this same proposed interface.
I have not purchased any of these, expecting that they aren't compatible yet.