Rahter than the "old" tack in the shoe, which can be defeated with sensor pad, or biting the tongue, which could seen. Why not this?
A small piece of wire between two of the top teeth on back side. When needed, just press tongue to this. Not nearly as noticable as biting.
Thoughts????
just from a medical perspective you run the risk of it falling out of place and swalling it/having it puncture something important.