Though I've been answering your PM, for the benefit of anyone else reading...
Each digital reading is an Accurite thermometer/hygrometer. I used the instructions on this forum (I think the DYI section) to rewire each one to have three probes: 2 for temperature and 1 for humidity. That allows me to put the probes inside the tub (hot side temp, cool side temp, and humidity), but keep the unit outside for quick and easy reading. I pretty much stop in to check my snakes several times a day to make sure everything is set up properly (maybe just a tad obsessive! lol but with the weather warming up I have to adjust the space heater for day time and then again for night time), and this makes it easier on me since I don't have to disturb the snakes or try to get the right angle to see the unit inside the tub. It also takes up less space inside the tub. I make sure each tub has its own thermometer/hygrometer too, just so I can measure individual differences, no matter how small, and make whatever adjustments are necessary to keep everyone comfortable, happy, and healthy.