I have heard a few stories about using ultrasonic rangefinders in caves - but unfortunately none of them were very positive.
A group that I've been surveying some lava tubes with tried out a hardware store one, and declared it virtually useless. It had a really short range, and needed a nice big flat surface to get anything like an accurate reading. They quickly went back to using a tape for most of their surveying. And if there are bats around, I would think you'd be interfering with their biosonar signals too.
Laser rangefinders are definitely more effective. I'll stick with my Leica Disto.
If you use a white target plate (or brown for longer ranges) to measure between stations, you can get hundredths of a foot accuracy for up to a few hundred feet with the common models. You usually get acceptable accuracy with side or ceiling shots without a target plate, too. Just avoid reflective surfaces like water, and take the average of a few shots.
You might do well to keep eye out for any cheap used Leica Distos on eBay...