Oh, I think that would have to be the past-life registry: you pay a handsome fee to have a sample of your handwriting put on record, together with a message and/or artifact intended for your future self, and stored in perpetuity. The guaranteed service is that when you (anyone) comes to do a search at some future time, you’ll be notified if there’s a handwriting match, and then your former self’s past-life identity will be revealed to you, along with the message and artifact.
So if you use the service to search among the handwriting samples of the registered deceased and there’s no match, you have to pay; but if there’s a match, you’ve already paid, so there’s no further charge.
Because of course if you are the same person, reincarnated, your handwriting will be the same.