The Prince Lionheart Slumber Bear sounds like the typical over-hyped nonsense targeted at new parents:

The Original Slumber Bear contains the ONLY actual intra-uterine, recorded womb sound to help lull your Baby to sleep in minutes!

The fact is, it actually works.  Norah was very restless any time we put her down in the cot and would only sleep in our arms, which wasn’t very convenient.  With the bear playing these intra-uterine sounds we can put her down with a soother after a feed and have a reasonable expectation that she’ll fall asleep.  It doesn’t work miracles though: if she’s cross or upset then it won’t put her to sleep.  The bear was mentioned to us by another satisfied parent whose twins were successfully being lulled to sleep.

The only downside is that Norah has to cry really loudly to activate the bear (by which time we’ve usually woken up) but if the bear is positioned near her, she’ll usually whack it and activate the motion sensors.  A pretty cool little invention really.