I thought in UK you could but now you cant
[ you can certainly put in a condition of a contract that the contract shall only take effect on the date of death of someone but that is hardly insurance ]
You can only do so in principle if you have an insurable loss in the death ( which most of us dont )
see here
http://www.easyretirementknowhow.com/articlecategories/life%20insurance/sya111003lifeins-CanIbuyforsomeoneelse.htm
otherwise you have to get the spouse to insure himself and then assign it to you
oh and the stories about Marilyn Monroe's clavicle being insured for $2m when she broke it, are tosh apparently ( and betty grable's legs ). Studio hype. YOu can't insure body parts like that - see above