A normally-proportioned person cannot effect changes on a haptic device (eg: Iphone, Kindle) with their toes. Toes are too far from the electric resonances occurring in the heart that drive haptic responses to allow an effective interface. You can discover this for yourself, while, for instance, shitting on your toilet while reading a Kindle placed on the floor in front of you. A page sweep attempted with either big toe will not elicit the expected response from the device.
Now: you know.