The Dance Fever is an okay invention. Although I think it would work and make dancing with people easier, it isn't needed to dance and not many people would be interested in purchasing the product.
The water bed womb is also a pretty good invention. It would be pretty comfortable and cozy. The only down side of the water bed would be breaking it like any other water bed. As well this invention isn't a very original invention considering that the normal water bed is a lot like the womb.