I’m looking for suggestions for low cost, battery powered temperature sensors. I will be placing these inside a few HVAC ducts to monitor supply and return air temperatures, so I won’t have any ways to run power to them. I looked briefly into the ESP8266 system, but it seems battery life would be an issue since it is wifi based.
I’ve also looked into some of the 433MHz stuff, but don’t have much knowledge of it. It seems with the 433MHz stuff I’d be pretty limited in how many sensors I can utilize as it doesn’t appear that they have unique IDs that they broadcast with.