Certainly a specific use case, but someone asked for an upload so here it is.
This tablet mount slides into the iFit slot on top of a NordicTrack treadmill and holds a Fire 8 inch tablet in a case securely.
The tablet should fit snugly otherwise it will flop off during use. I uploaded the f3d file in case you want to modify the tablet bracket to fit something other than a fire tablet. You should just need to modify the length of the “tablet holder back” sketch. (Some day I'll learn parametric design…)
The author marked this model as their own original creation.