i would also say Herpstat. If you can splurge, go with the Spyderweb 2 - it connects to the internet, and can notify you of critical temperature changes. It has 2 probes, so you can monitor your room also. (and if not needed now, may be something to use in the future.
Having said that, I have some basic Herstats that are 10 years old, still working well. I can't unfortunately say that about the VE's I have had in the past.
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