re: Server room environment monitor... any suggestions?

Seconding the thanks. Any other suggestions for something simple?

I had a small server room overheat this week due a failed condensate pump on a mini-split. The control for "Mr Slim" -- yes, that's Mitsu's name for it -- can display all sorts of diagnostic and alarm codes, but the first-level HVAC service guy and I couldn't find a port for an external alarm output or contact.

So... I too am looking for a simple-and-cheap over-temperature alert. Was thinking about putting in an Ecobee Lite stat just for its ability to send alerts, but if I'm going to DIY for just one condition, cheaper would be better.

TL;DR: anything cheaper?