Dead Man's Switch - A website that allows you to send a message to 1 - 100 people after you haven't checked in. Allowing for those on your list to receive a last message from you.
There was an episode of one of those crime shows that revolved around a site like this. Except it was the rapture not individuals dying. Iirc if the owner of the page didn't check in for 24 hrs it sent all the emails. He got murdered all the emails got sent out and one of them was a murder confession. Weird episode, I wish I could remember which show it was. Feels like a CSI episode
As I mentioned in another comment I was thinking about this sort of site the other day and this is the other major issue that occurred to me. Not to mention that if they can send it, they can read it - or you have to encrypt yourself and prepare your recipients.