I always take my drivers liscense with me on shore. I would say that at least 98% of the time the guard at the entrance to the port asks for both cruise card and photo id and we have only cruised in the Caribbean.
I don't think that the bags with the cable in the strap is over kill as I have seen them online and they look like normal bags.
Caribbean Trip Reports
Star Princess 2005, Sun Princess 2005
Caribbean Princess 2006, MSC Lirica 2006 , NCL Pearl 2007, Majesty of the Seas 2008, Carnival Destiny 2008, MSC Lirica 2009, Carnival Valor 2009,Carnival Legend 2010, Carnival Liberty 2010,Carnival Fantsay 2011,Carnival Valor Feb 2012, MSC Poesia Dec 2012, MSC Poesia April 2013, Carnival Legend Nov 2013, MSC DIVINA Jan 2014, MSC Divina Oct 2014