I'm kind of afraid I'd forget about the dead man's switch that I've set up, only to one day find all my files wiped away. It could very well happen. Maybe for something like browser history etc you suggested it would work great. Pair that with a crypted drive where all the files you want to get rid of reside, and you'd be all set? So that when your relatives donate your computer to Goodwill, your pictures and text documents are not there for everybody to see.