Sara Blakely built her $1 billion Spanx empire on innovative design. With Sneex, a new sneaker-stiletto hybrid, she’s trying to do the same for shoes. For a decade, cutting edge fashionistas have strutted in high heel sneakers. Rihanna was a trailblazer. She’s frequently seen in high heeled Puma creepers and boxing boots, often made in collaboration with her Fenty label.