Was playing around with physic bodies in iOS 7 Sprite Kit, and the biggest problem I have is working out when and why the objects collide with others. Tried to work out a way to show the debug borders of each objects but keep failing.
Finally found this excellent tool PhysicsDebugger by ymc-thzi today, it's free and really easy to use. I don't have CocoaPods so just by manually dragging in a few files, include a few lines and it works perfectly.
Sample screen below from my iPad 2 using demo project with some slight modification - just added a few more objects and labels. Strongly recommended!!