The windows have a perforated metal plate at the base of the windows (at least in a bedroom). I came up with an idea for keeping a tablet or smartphone in place using a couple of machine screws inserted in two of the holes. I tried it out during my recent travels over the past two weeks with good results. Out of my junk box, pulled out some #10 machine screws (5/8 and 7/8 inch, just happened to be that length), washers and nuts. The #10 screw JUST fits into the hole with a little wiggling around. Next time, I'll try #8 or 4.5mm machine screws. Both lengths worked although it appears a 1/2 inch length is sufficient. The nut and washer provides a "lip" spaced above the surface of the plate which helps keep the tablet from bouncing out. The attached images will provide help clarify my description.
My wife used a pair for her smartphone and I used a pair for a tablet as illustrated. The spacing between them may be adjusted to fit the device.
My wife used a pair for her smartphone and I used a pair for a tablet as illustrated. The spacing between them may be adjusted to fit the device.