@davycro just said "it’s a tough skill to learn without a solid background in anatomy". If you have your home ultrasound and cannot accurately locate / track your baby, you may identify the wrong thing, and worry "it's not moving!"

Our first child came very late, and in those last weeks we downloaded a "baby heart monitor" on our iphone - it simply used the microphone with some isolation / amplification. We pressed the microphone end of the phone into the abdomen wall, and when it works we heard an amplified heartbeat out the speakers - very reassuring. But when it didn't work - when we couldn't find the heartbeat - we worried. Is it a false negative? Or should we rush to the hospital?