I keep the books for a commercial HVAC company and they have some nice digital commercial Thermostats (like used in the food industry) with accurate probes. My boss and friend offered to rig one up on my rack I am fabricating. (although what that really meant was "while I do this, you can fab duct on your day off") He has his master mechanical, Im sure it would work. But when I think of the snakes and the incubator...I for sure want something proven in the reptile industry, even though the money saving would have been nice. I personally went with Herpstat.
Really the best choice when you think about what is at stake. There are other ways to cut corners on a incubator. The thermostat is the one that you really want to play it safe with imo.