Well I don't have anything I know is completely accurate to test it against, but when I got it I shoved the probe in my armpit for a while and it gave the correct reading for body temp, and when it says my basking spot is 108 or thereabouts the babies will go sit on it when they wake up and after they've eaten or had a
bath, and spend the rest of the time slightly further away from the light on their branch in the middle of the tank, so the temps it gives certainly seem accurate enough for them to display normal behaviour.
And the other day when my roommate got a new beardie who was constantly scratching at the glass to get out and seeming very unhappy, it showed that the *****s we got him from had put a bulb in that let his temps get up to 145 (or more, when he checked after 5 mins that's what it said so he immediately turned the light off)...he's certainly calmed down now we've changed the bulb, poor guy!