We were recently generously donated some iPad Motion Mounts from a company called iCymbal. They are a hard plastic grip style backing that secures to a flexible arm mount that can be attached to any surface. They come in a variety of colours and with 2 sizes of clamping arms.With the shorter arm you can remove the clamp from the arm and use it as a tripod on any flat surface.
We have them in a few of our classrooms and have found that they really can be mounted just about anywhere. The mount is very secure and when tightened the tablet does not move. It can however be rotated and positioned to however you need it to be.
I have been using one at snack time with a young student. The Motion Mount is clamped with the short arm to the table and the tablet is positioned just right for his reach, off to the side where it isn't not getting in the way of his snack. I have also been able to adjust the angle of the tablet to reduce glare and have the images presented clearly and in his line of sight.We have also used it as you see in this picture while working with some of our other apps.
I found with the shorter arm length that it was a bit more difficult to position on a stander or wheelchair and have the same range of tilt and positioning options. It worked great for an app that students were watching or listening to. With the longer arm you would be able to have more positioning options for students with restricted mobility or limited vision.