We do some kicking with the toes, usually because we're aiming at a vital point. Ever been big toed in the 'taint? You can't imagine the pain. I believe they do it in Savate, but I think they have nice pointy shoes to do it with. But I've seen a lot of liver shots in Savate matches. Maybe Cord can confirm or debunk that theory.
Anyway, it's a tool that can be used for sure. It's just a question of whether or not you think it's worth the time and pain to create this one very specialized tool. Sorry, no shortcuts...start breaking them toes.