Sure, you could spend hundreds (or even thousands) of dollars on a high-quality mini projector for your smartphone. But, with a little ingenuity, a shoebox, and a magnifying glass, you can make your own projector. It may not look as good as one you buy from a store, but it’ll do in a pinch.
With a shoebox magnifying lens, and a few other crafting items, like glue, foam board, and cutting tools, he built a projector that comes with its own smartphone mount.
It is a simple project, and something that would be great to do with the kids, especially if they are learning about light reflection and refraction in science. You can discuss why your smartphone has to be flipped upside-down in order for the image to appear right side up on the wall.
The image quality is far from superior. However, speaking from experience with the $20 Cardboard Smartphone Projector, I can say that the quality is comparable and you will probably spend a lot less on the materials if you build one yourself.