I am guessing people may already know this, me I didn't have a clue but thought it was quite a good idea!
Travelling back from London this evening, train packed, when a young man sat in the seat next to me. He got his phone out and head phones and attached the phone which was in a case onto the back of the seat that was in front of him and the phone just stayed there. The magnetic bit on the case held the phone whilst man sat and watched something.
I waited for him to get off and tried mine and it worked too! Trouble is when I am out and about I never watch anything on my phone just listen to audible books.
I think I am easy pleased! 