Have been thinking I really need to implement a strategy for securely storing all my online usernames and passwords in the event something happens to me, that my better half can get someone to help her log into those accounts and take them over. 

I'm keen to here what others have done on here.  Also, if you've got 2 factor authentication turned on, how you cater for this (assuming that if something did happen to me, my phone gets destroyed in the process).