Yea, it's a nst, non stress test. They are used to measure baby's heartbeat and reaction (they want to see a base line and then baby's heartrate spike up and come back down). You lay on a bed with 2 sensors on you. Very relaxing to listen to babies heartbeat actually.
They are common for anyone with any type of complication, like high blood pressure, diabetes, being obese, having more than 1 baby, and the list goes on.