This might as well be called "ProfilePictureImageView", but that's no bad thing! If you need to display a photo of someone in your app, being able to detect a face is far easier to use than any pan/scale/crop control you could build. This library from Beau Nouvelle gives you an image view that'll find and centre a face in a photo. Really smart use of face detection technology.
Not being involved with anything which has needed SceneKit, I wasn't aware of exactly what it was capable of these days. Avihay Assouline gives us a run down on the new Physically Based Rendering features. It's pretty impressive.
I can see that with iMessage apps now being a thing, that it might be the case that the ability to write with your finger, or draw small doodles might be a bigger requirement than it used to be. Rather than build that yourself, here's a pre-built component.
Talking of iMessage apps, Prianka Liz Kariat gives us a walkthrough of creating a tic tac toe game inside messages. I'm not sure these apps are going to be a huge success, but I bet we'll see at least a few really catch on, especially when they integrate with a full blown iOS app.