It’s called military surplus Velcro. You get a second rubber case for the tablet that you apply Velcro to the back of then apply the other side to the treadmill

It’s called military surplus Velcro. You get a second rubber case for the tablet that you apply Velcro to the back of then apply the other side to the treadmill in an area where it makes full contact. I have seen videos of people in Velcro suits jump and stick to walls so I’m sure it would work with a tablet.