Interesting ideas here. There is a ticket in Bugzilla about providing owner information on the lock screen: https://bugs.maemo.org/show_bug.cgi?id=793 , but as these ideas here go further it might be worth to file a ticket in Brainstorm (Problem: "Thief detection") and to file the solution(s) that come up to your mind as separate solution that people can vote for: http://maemo.org/community/brainstorm/