Made my own with raspberry pi and relay. Updated version is a esp8366, which is a wifi micro controller speaking to a reaspberry pi over mqtt. Around $35 all up either way and has never been more stable.
I'm using inkbird thermostats.
They are very accurate and price is affordable.
There are only on/off available but for heat mats or cables just work fine.
The ITC 1000 will do the job.
