Sherlock lets you edit views and layout constraints in real time, simulate running on other devices, and jump straight to the source code, all from your iOS Simulator - zero configuration required.
Incredible tool allowing us to change the design (including constraints & custom IBInspectables!!!) without rebuilding. Literally amazing!
Pros:live updating for custom @objc, and @IBInspectable, and even for constraints!
Cons:I mostly finish up design changes on a real device, instead of the Simulator, but I cannot do that using Sherlock :(
eGov