There are the infamous 'dead pools' or 'death pools' around the net where you pool your money together and whoever predicts the most deaths/the unlikeliest deaths in a certain time period e.g. one year, scoops the cash. Most though are free-to-enter with no prizes on offer.
No such legal bookie exists that would strike a bet with you about the odds on anybody dying.
I remember on a BBC2 late night documentary series on gambling not too long back with an episode centering on 'wacky bets' where Graham Sharpe was asked about whether he would give odds to somebody who asked about the odds on someone dying and he said that
William Hill's wouldn't on the grounds of 'bad taste'.