Are they the ones that have magnets in the boots & stirrup treads? I think they hold your foot there but if something major happens your foot comes out of the stirrup easily.
She developed them with Swedish manufactirer Tretorn, and they have become HUGELY popular in Sweden - Malin B-J is a big rolemodel to young girls. Everyone over there wears these boots now.
I think these may be the new stirrups and boots that have been designed like they use for cycling. The boots have a metal plate on the bottom which locks into the stirrup. However, if you twist your foot they come away.
I read about the new design a little while ago, but have not seen them in use.