Neocubes are a relatively new addition to the science toy market. A neocube is basically 216 small spherical neodynium magnets. They can be assembled as a six by six magnet cube, but also as many other shapes and three-dimentional structures.
There are numerous videos on the internet showing the many different forms they can make up. It is actually astounding how many different things you can make with these small simple magnets. From cuboids to spheres to long chains or band that can be worn as jewelry (necklaces or bracelets). They have already provided me with many hours of entertainment, and they still haven't become boring, as most toys do. There is probably no limit to the things that can be done with this toy.
I believe that it would also make a very good stress relief toy. It allows you to use energy to break the bonds between the magnets, to crush shapes in your fist and to get creative with the forms you can make with it.
However, I would not say that this is a good toy for children under 14 as, if care is not taken, the magnets can be easily lost or swallowed (by very young children).
They can be bought online from a number of companies, which sell them under different names including Neocube, Buckyballs and Zen magnets. For
More info at Neocube and Buckyball websites.