Coincidentally I've tried it briefly yesterday at the end of a darkroom session, just for fun, and failed miserably...
First tried a contact print, which became one blurry mess. Possibly due to the glass screen protector on my phone, increasing the distance between lcd and paper too much.
Then I put my phone in the negative tray of my enlarger and my touchscreen went bananas on me. Ghost touches made it impossible to keep the inverted image steady on my phone.
I didn't make any serious attempts, just wanted to see what would happen. Perhaps some kind of plastic spacer could be of help here, but it was already late so I called it a day.