Hypnobirthing app I have is called innervision. Let me know if you can't find it and I'll seek out a link. It's quite similar to the Rainbow Relaxation CD we got as part of our hypnobirthing class.
It's got different relaxation tracks - for early pregnancy, mid pregnancy and during labour. I've only really listened to the mid pregnancy one and we usually fall asleep to it. I've not listened to the birth one yet but imagine it'd be good for early stages as that's when I used the rainbow relaxation one last time. It's not that long, though, and as my first labour was 3 days (from first regularish contraction) I found there were only so many times I could listen to it, so good to have other things up your sleeve too!
I do have mixed feelings about hypnobirthing - I think relaxation is extremely important and can help have a better birth experience but I also think it can raise expectations (eg about painfree births - which although I believe they are possible, I also believe are rare) which can make women feel they've failed if birth doesn't go that way. My HB class wasn't like that at all, the teacher was very down to earth and realistic (she'd had 5 babies, not all using HB), but I think the book can encourage you to be a bit too rigid in your thinking and planning. Personally, being more open minded worked better for me, while using some of the hypnobirthing techniques.
Sorry for the essay!