I was thinking a thread where we could do product reviews might come in handy. Many things we use may not be designed for our Thamnophis friends but sharing the good and the bad of these products might save someone money and a headache. It also shares the great ideas that are out there.
I'll get things started with this:

Digital Heat Mat Thermostat by Hydrofarm Horticultural Products. Hydrofarm - Grow Lights, Hydroponics and More for all Your Horticultural Needs! I purchased mine off Amazon for under $26.00 delivered. Model MTPRTC

It is made to control 1 heat mat. It is rated at 1000 watts max. Mine is controlling a 12" long section of 11 inch flexwatt.
I placed the temp. sensor under the substrate. Setting it up was easy. Adjusting the max. temp you want the heat mat to reach was very simple. It will reach the max. temp you have entered and turn the mat off. Looks like the temp drops 3 degrees then it cycles on again.
There are other thermostats out there, some that control up to 4 mats at a time but they are in the $350-$400 range. Granted these other thermostats have alarms built-in and other features but they are pricey.

I feel this is a very good entry level device. I personally would rather buy 4 of these for $100 and at some point probably will. It comes with a 1 year warranty so be sure to keep for paper work.