Over the last year and a half I have used a number of termprsture sensors - official ST. motion sensor, iris, monoprice, st button. So far at one point or another they become entirely unreliable in updating themselves - it’s random based on placement and device, what seems to work much more consistently are other devices that talk to ST via API (nest thermostat, tado radiator valves etc) can anyone recommend an inexpensive device that can consistently and reliably feed temperature info to ST.
I think history has shown us that there isn’t anything that can operate “consistently and reliably” on SmartThings. The platform itself is unstable. As the company says in their official product usage guidelines:
Data accuracy and consistency from SmartThings sensors, including those provided by SmartThings directly, resold by SmartThings, or supported by SmartThings, is not guaranteed. Therefore, you should not rely on that data for any use that impacts health, safety, security, property or financial interests. For example, because temperature readings may vary significantly from reading to reading on an individual device, between devices, or over time, those readings should not be used to control heating and cooling in environments where food spoilage, health risks, or damage to physical goods could occur.
That said, I think people have had better luck with the purposebuilt temperature monitors, rather than the ones built into the other sensors.
I don’t think much has changed since the following thread
by the way, I would guess that pretty much any mains powered device would be more reliable than any battery powered device in the under $100 price range. So you might also take a look at the homeseer plug-in multisensor: