Best Temperature monitor that can be remotely monitored

Anyone have a favorite remote temperature monitor for their RV?

I am looking for something that would send me an ALERT to my cellphone perhaps via going onto my WIFI hot spot I would leave at RV and would then relay the message via e-mail or SMS Text or something to my iPhone over cellular so I could be miles, states, or countries away at the time.

I have been considering the CANARY PRO, which would also be an alarm system.

I would prefer something that didn't require a third party in-between... or at least one less likely to go bankrupt.

For example if there was a monitor that used SMTP to relay to GMAIL and that account sends me the e-mail.

Anyone have something they recommend?

Thanks

Chris

P.S.  I have looked at many of the solutions popular RV'ers on YouTube use, but most are monthly subscriptions through alarm services, and I don't need something quite that secure e.g. SimplySafe or RING