It's interesting that there are essentially no pictures of the actual device anywhere on this page (except for a lone image, from the back of a user's head, where all you can see is the strap and the edge of the front).
Ankles can be tricky. Most "barefoot" style shoes have essentially zero ankle support. What ends up happening for most people is that if you ease into them, and use them regularly, you end up building up substantially more muscle in your foot and lower leg which ends up being the "thing that gives you ankle stability".
If you've got really serious ankle problems / past injuries / etc, that might not be a plausible approach for you. But if it's just a case of your ankle being a little unstable every so often, it might be worth trying the barefoot shoe approach, and treat it like building up new muscles in any other context: start slow and easy and try to be consistent about it.