somethign sofisticated and high hi-tech that it is connected with you with a chip under the skin, this chip is connected to a safe box, that it will open if you die or if commanded
in the safe box there are your bitcoin in a paper wallet or usb stick
Biochips are under developments and research now, so I think it would probably be a thing in the future. Also, those biochips would certainly be a form of security when it comes to financial talks.