I wanted to do a hyperlapse of printing but I needed a cell phone mount for my tripod so here's the end result which seems to work really well. I designed it to fit a phone as small as a gen 4 iPhone or as large as a LG Turbo in a beefy case.
Update: I improved the screw to prevent the top from pivoting as much. This will make for a better fit on the phone
IMPORTANT: This print requires a 1/4 - 20 nut which should be cheaply available at any US hardware store. This is needed to mate with the standard tripod screw
CAUTION: This is meant to hold a phone on a stationary tripod. I wouldn't trust it on something moving. For a moving tripod, get an action camera mount instead. Also, please have this assembled and nearly adjusted BEFORE inserting your cell phone especially if you are on a hard surface such as tile or concrete. Please be responsible with your expensive cell phones.
Either print the STL with all parts (Cell Tripod Mount)
Print 1 base, 1 top and one screw.
If you're screw threads are warping up, try turning down the bed temp after the 1st layer. This made a big difference for me on printed threads.
1) Insert the nut. I didn't need to glue the nut in but you might if you have a very accurate printer.
2) Screw the base onto the tripod
3) Thread the screw through the top
4) Screw the top on just enough to have room to insert your phone
5) Tighten the screw till the phone feel secure