Because heat and (low) humidity are central to Russian tortoise health, accurate monitoring is the most valuable technology you can add to the enclosure. A reliable thermometer at the basking spot and a second at the cool end let you confirm you actually have the gradient the species needs rather than assuming it, and a hygrometer tells you whether ambient humidity is staying in the dry range that suits this arid-adapted tortoise.
Digital probe thermometers and combination temperature-humidity meters are the practical workhorses, and a non-contact infrared thermometer is invaluable for spot-checking the exact surface temperature of the basking area — the number that matters most and the hardest to gauge by feel. Reading several points rather than one gives you the true picture of the gradient.
The payoff of good monitoring is catching drift before it becomes a problem. Lamps age, room temperatures change with the seasons, and a gradient that was perfect in spring can be wrong by midsummer. Instruments turn husbandry from guesswork into something you can verify at a glance, which is exactly what a species this sensitive to its thermal and humidity environment requires.