Yes, Trevor is the frog from my avatar. That was a baby picture though; she's about twice that size now

Okay, that's good. That's what I've been doing; the air temp is usually pretty hot compared to her substrate during the day, and about the same as her substrate at night. Like, today the ambient temp was 85 and her substrate was 75, and last night the ambient temp was 77 and her substrate was 76. She seems to like the cool side of her cage right now.
The thermometer I have is actually an infrared (it was very late when I wrote that... apparently I forget what type of equipment I have when I'm tired) There's no gauge, you just point it close to whatever you want to take the surface temp of. I've heard these can start getting inaccurate near the end of the battery life, so I'm keeping an eye on it.