considering at least two islamist attacks in germany by a refugee have been carried by a minor[1][2], i don't think that fingerprinting refugee minors should be out of the question -- though obviously the details should be carefully deliberated.
there is absolutely no way that mandatory government spyware on phones will guarantee effectiveness, though -- the bataclan attackers for instance used ordinary sms to coordinate[3]. besides that, the potential for abuse is unfathomable.