New API allows apps to send text messages without user interaction

Critical Messaging API requires user's permission though

New API provides a way for app to send SMS to specified phone numbers. This might be useful to provide check-in functionality in areas where cellular connectivity doesn’t allow internet access.

Important considerations:

• App needs com.apple.developer.messages.critical-messaging entitlement

• App must declare NSCriticalMessagingUsageDescription key
  in app’s Info.plist

• App must request authorization for each phone number using through requestAuthorization(for:)

• send(_:to:) method only works if the app is backgrounded, if it’s called from foreground the framework returns a MSCriticalMessagingError.notSupported error

• The system may impose a rate limit on frequency of messages sent

Apple Developer: Sending SMS messages from an app

Reference:

• Your iPhone now lets apps send you ‘Critical Messages’ via SMS