UK mobile phones are to get new emergency alert feature. Messages will be triggered by UK Government or Emergency Services (initially focussed on serious weather-related events) and target people within an affected area. Only sent if there is an immediate risk to life (so hopefully won't get one in earnest ever or at least not for many years).
However, there will be a test of the system across the UK in the early evening of 23 April 2023. Phone users will have to acknowledge the alert before they can use other features on their phones.