I like the idea. I'm sure that if it were to happen it would be a USD to BTC equivalent. So instead of a flat rate of x btc, it would be a rate of x usd then converted to btc. 
I guess you could do that now with a will and a executor of estate.  Will that your policy pay out must be used to purchase btc and then distributed to your dependents.   
It will hopefully make your dependents more likely to save it, rather than blow through it.
It's worth looking into.