Edit: …in an automated fashion. For example, is there an app where I can put an object on a turn-table, point my phone at it, and give it a spin? (Clearly that would work only for certain shapes.)
For something like this, use a contour gauge at certain offsets from a set point will give you a set of curves you could model through.
You can, if course, just measure and draw it out yourself. But the rounded sides are likely going to be guesses.
So, major kudos on this release. Could probably just sketch in blender and then just standard difference tricks to put your case on one of these.
Use a caliper measuring device and a flatbed scanner.
With the flatbed scanner, make a high res (600 dpi, or maybe even 1200 dpi) 2D scan of the front of the phone. Keep the screen of the phone on while scanning, and have it display some image that contrasts well against the edges of the screen, so you can clearly see where the edges are. (Ie if the phone is black or other dark color, use a an all white image. If the phone is a bright color, use a dark image.)
Scan the back of the phone as well, so you can see where the camera lenses on the back of the phone are.
Import the 2D images into your 3D modeling software of choice and create a flat polygon covering the front view. Extrude into a 3D shape.
Scale according to physical width, height and depth of the phone that you measure with the caliper.
Make room for the lenses using the scan of the back of the phone.
Buttons on the side and charging port on the bottom you can decide on how to fit from using caliper measurements, and adding some additional room around those as that is often desired.
Then model a shell that fits around it.
It will probably take a couple of test prints and refinements to get it right even so, but I think said approach will work well in terms of benefit to effort.
That’d work pretty well for phones (like the PinePhone) that are basically “rectangular prism slabs with uniformly rounded edges and corners”. It’d be much harder to model this Samsung S4 I have here, with its curved ends and it’s compound curved back…
Take a photo of the object from all angles, I usually end up with 40 photos. Don't move or spin the object, the static background details help align the images and you want the lighting to be consistent. Smartphone cameras actually work best for small objects because their tiny aperature keeps everything in focus.
I've used the turntable laser scanners (NextEngine specifically) but it is far from automated, requires hand alignment of point clouds. Photogrammetry approach was much lower effort.
But really this gives you a mesh, which is far from being a CAD drawing. Taking measurements and drawing from scratch is usually how I've seen it done when accuracy matters.
You touch the object in as many points as you need and translate the touch coordinates from the angles of your tool's arm to XYZ. Or some systems allow you to do it optically.
I've worked with these, they are super cool. Just the laser part of the hand-held scanner was detailed enough to show the lettering on a laptop keyboard because of the differing depth of the molded-in characters.
Here's a random video of someone doing that: