I am hoping to find a water temperature sensor for my pool. Is there something like this available? I had made one using a raspberry pi a few years ago but it stopped working and I don't want to mess with it again.
Just bear in mind that you will need an ecowitt WiFi console, or either of their WiFi gateways (GW1100 or GW2000) to use it with Hubitat. I linked to the GW1100, which is their cheapest WiFi gateway.
This sensor works with the EcoWitt gateway devices, so yes, you will be able to access the data in HE for use in automations, and, if you want, via Maker API for external systems to HE.
Yes. Any sensor that pairs with the ecowitt gateway will be exposed to Hubitat to use programmatically, as long as you use one of the two integrations indicated above.