The battery life of the moisture sensor is about two days as far as I can tell, at least with the "battery life" indicator switched on. Furthermore, the WX1 tap timer battery cassette has extremely thin and weak battery contacts that bend easily and give poor connections - leading to an "offline" indication until you remove the batteries and rebend the contacts.
It's a pity that the Holman Wi-Fi system doesn't (so far) live up to the quality standards of the rest of Holmans products. I hesitate to label it useless consumer junk just yet. No matter what features and how convenient it is, if it isn't reliable then that's what it will be.
My gardens have cost me many thousands of dollars and countless hours to establish. We live in country Victoria where it gets very hot in summer. I MUST have a reliable watering system for when I'm many miles from home. If this stuff doesnt work reliably, then its back to the less convenient Hydrawise system.