Wolfram seems to keep a searchable index of all his keystrokes.

From the 12 December 2009 issue of New Scientist:

"I'm an information pack rat," he [Stephen Wolfram] confesses. Recording our interview is just the tip of his peculiar obsession with documenting every moment of his life. "I have a keystroke logger that has collected my every keystroke for the last 22 years," he says. "Every day I get an email that tells me how many keystrokes I typed the previous day into each application. I find it slightly interesting." He shrugs off my suggestion that it's a way of securing his immortality; he believes that soon everyone will be doing it.

That sounds rather Nixon-esque.

Which, if any historians become fascinated with Wolfram, would be an amazing boon.

Weird then that he regularly uses an iPhone and iPad which presumably don't offer this functionality.

He once said that he records all of his own keystrokes(Sorry don't have the link). You need to remember he is a very unusual person.

A keylogger, recording all keystrokes.

Like this one at the kernel level http://code.google.com/p/logkext/