A developer tool to enable access to iOS’s built in UI debugger tool. Refer to this blog post for details on the features.
The default Activator gesture is a double-tap on the left side of the status bar. When an app is active, it will launch within the app. Otherwise, it will activate within SpringBoard. Note that this is accessible from the lock screen by default. If this is undesirable, configure Activator to not activate from the lock screen.