I have hired one from First Beats for $40 a month - it is reassuring to be able to hear bubs' hb especially because I lost my first bub at 8 weeks, but the hardest part is not using it all of the time! I quizzed my midwife about the safety of them, and she said that nothing has been proven in terms of them being unsafe, but she wouldn't recommend using it more than once a week (if that). I have also found that even at nearly 18 weeks, I don't always find bubs' hb straight away - so if you are a born 'stresser' like I am, you need to be able to stay calm and not freak out if bubs' is hiding