I have used the TacX tablet holder for several years to hold a standard sized iPad while stationary training. The only annoyance is that when in use the iPad is held very slightly off of straight on. Not in any way that detracts from its purpose but just enough to be noticed (at least by me).
It can accommodate tablets from 197 x 112mm up to 267 x 182mm. iPad mini is 203.2 x 134.8mm so no problem there. However, the bracket is too small for a large sized (12.9in) iPad pro.
BobS