Toning shoes are a similar concept to these:
Only instead of increasing your vertical leap/sprinting, they cause you to activate more muscles to remain stable, when used properly you can duplicate the resistance of walking in sand.
I'm a total fan of New Balance, btw, only pair of shoes I've ever bought for more than $40 that I felt were worth more than I paid for them. Got normal length feet for my height, but the ball of my foot is oddly wide, makes me extra tough on shoes.
The NB's + Dr. Scholes massaging gel inserts have lasted for several years and are still just as comfortable as ever, and don't look ratty or anything either.