Have you seen these?
Add to Cart
It's a monitor that you can use to hear your baby's heartbeat anytime. Mine came with 2 headsets. I remember waking from a nap while pregnant with our 3rd (and last!), and our other two kids were standing beside my bed, monitor in hand, headsets aleady on their heads. They were going to listen to the baby while I slept. It does pick up all kinds of other noises, so it can be tricky to find. But it's kind of fun.