Early last year I mentioned a handy library allowing you to overlay a grid on your user interface to aid in design called Grid-Window.
Here’s an open source tool for creating configurable overlays according to your design specs inspired by the dspec library for android called dspec-iOS that adds more configuration options than the previously mentioned tool.
With dspec-iOS you can overlay a grid over the interface based on your specifications, with configurable keylines, baselines, spacing markers and more so you can quickly see if your user interface is aligned with your design specifications. Specs can be loaded from a JSON file if desired.
Here’s an image showing dspec-iOS in action:
You can find dspec-iOS on Github here.
A nice tool to aid in interface design.