This tip is if you work with Core Location and wants to continue receiving location updates while the app is suspended.

You need to add the UIBackgroundModes key with value location to the app's Info.plist. In addition, — this is easy to miss because it was only added in iOS 9 — you want to set CLLocationManager's allowsBackgroundLocationUpdates property to true. In addition to getting updates while the app is suspended, if the app is killed and the device crosses the CLRegion you are monitoring, the app will be automatically launched. So this property is also useful for toggling that behavior.