This is a product that is getting a lot of traction in Australia where it was developed and where they call this type of footwear, thongs. They are commonly sold in podiatrists offices and are proving quite popular. The amount of arch support built into them is about the same as you could get in a prefabricated or over-the-counter foot support. You can often see comments that anyone who tries them on, buys them as they find them so comfortable.
You can read more about them here and buy them here.