I am doing this but fixed the probe on the outside of the pipe. No need to insert it into the pipe. Pool temp, water to solar heater temp and return temp.
They opened it. Currently a BETA release.
API Documentation
Requests
The Olarm API can be accessed by sending requests over HTTP using GET and POST methods.
Base URL
https://apiv4.olarm.co/api/v4
API Key
The key can be passed in an authorization header.
Authorization: Bearer APIKEY...