I was thinking of phones and tablets while chewing on a Lego figure as you do.
This led me to creating hands for Lego figures that can hold stuff properly. Not only phone and tablets but books, newspapers and cards that you can print yourself.
There are two designs both have the opening turning in. One design is the same dimensions as the existing hands but turned and the other has closed hands with a 0.25mm gap. Because they are printed in white and black flexible you can put anything in with a thickness of 0.25 to 1.50mm as you can see in the picture with the penny. The hands look big in the picture, since the picture was taken the hands have been reduced to be closer to the original size.
I'm not sure how many I should put on a sprue so please let me know how many you would like and I'll see what I can do?