Mark me down on the cynical side, but I don't think I want someone sticking one of these on my ancestor's tombstone.
1) Who decides which descendant gets to put it on?
2) Is it going to permanently mark the stone in some way?
3) Will it work in 50 years? 20 years?
Here's one site. There are others.
I'm not opposed to preserving memories and information. I'm just not certain this is the way to do it.
Punch cards? Floppy disks? Who can say this is any more permanent?
Publish your genealogy and preserve that. I'm certain others will disagree with me, but I'm just not certain this is the way to go about it.