I made a mistake buying one of those apps it said some people have success from 19 weeks as I'm passed that thought it was worth a try, less messy than my doppler when we wanted just a quick listen in as she's moving everyday pretty much now.
But its never worked not even for my own heartbeat and when I complained they said it only works from 28 weeks :s
I downloaded one called babyscope and I didn't hear anything, I don't know if you could take that to mean they work or not.
Sorry I couldn't be more help![]()