Don't hold your phone whilst driving - you'll wind up killing someone and going to jail. Instead, get a cradle or print this one for free! This is a great little iPhone 6/6s car cradle that clamps onto your heater vent. I just tested it out and it works fine (naturally, some modification may be required for the vents in your car). It is light weight, uses minimal filament, gives access to Lighting port and audio jack (provided your plug isn't too big), doesn't require any drilling to your dash or dirty suction cups on the windows. The unit comes in two parts: the Phone Cradle and the Vent Clip; these slot together (the fit is very tight though so some filing is a good idea). This is great because if you print it and it doesn't fit your car, you don't need to print the whole thing again - just the modify the little vent clamp and reprint that.

If you do print it and it slips off your vents, you can always try wrapping some tape through the slot and around and around until you get the thickness you need for a snug fit, that's the easiest way. If it doesn't fit because the Vent clamp is too big, you can open it in Fusion 360 and use the Modify > Combine tool to subtract geometry you don't need. Or just file it down with a trusty nail file if you are not so technically inclined!

Fusion 360 file is included as always for anyone wanting to mod it or remix it properly.

Recently modified: Photos show V1. New height is now 75mm for better stability and T slot should be easier to fit in without filing.

Monoprice Select Mini or Malyan M200

Yes

Yes

Any res is ok, I printed it on 0.1mm layer height and seems to work well.

30% triangle

With both parts, be sure to check the box in Cura to "allow support material".
Use the layer view slider to visually inspect and confirm that the support structure is decent.

Using a small brim of 5mm is recommended to avoid the parts falling over.

It's all sketches, extrudes, lofts, combines.