Read-Once Messages?

[Lefty]

Has there been any work done on messages that can be read a single time,
preferably only by a designated recipient, and is not amenable to being
captured as it is "played"?  I know that Gibson's poem _Agrippa_ had some
sort of self-destruct feature built into it, but I don't know what
mechanism was used to implement this.

Any pointers or suggestions would be appreciated...

--
Lefty (lefty at apple.com)
C:.M:.C:., D:.O:.D:.