I just got back from the non-stress test, and the baby's heart rate is fine. In fact, he was very cooperative. They like to see the heart rate go up and down several times, which typically happens from movement (although it can happen for other reasons, too). He was doing his typical after-lunch dance, where he gets very active starting about 10-15 minutes after I eat and lasting up to an hour or more. So they got exactly the sort of readings they were hoping to find.
They sent me home without any further testing. So now, it's back to the waiting game (and my afternoon nap-time)!