A common mantra in the yoga community is to "spread your toes" during various positions. The spreading of toes is believed to spread the bones and tissue of the foot to better align the knees, hips and ankles, providing better balance, movement and flexibility.
The Yoga Sandals takes this concept to the wearer by forcing you to spread your toes as you're walking. Each toe is separated by a plastic-covered piece, similar to thong sandals but for every toe. They are a counter option to the pointy-toes shoes that squish toes and feet together. Yoga Sandals have been used by spas for years for pedicures, although haven't been promoted as everyday wear until more recently.
See also the Fit Flop for a sandal that wants to improve your life by changing the way you walk.