It's no big deal. Programs have been around for as long as I remember that can take an image and turn it into letters. Just someone took that and make a program that could do it with movies. Obvious really. Search the internet. I did the same years ago and got a load of static image convertors, although nothing existed for movies. Not too difficult to work out though as movies are just lots of still images. Heh, I remember we used to get them working on Sun Sparcstations (before we found and compiled JPeg and MPeg viewers). Then (on 21inch screens) we used to reduce the windows down to miniture level (would scale properly), and then you had a nice mono image appear when the letters became pixel size. Defeated the point really... anyone remember the famous Snoopy picture?
Still, like you said, it still looks really cool.
Cheers
I am 99% probably lying in bed right now... so don't blame me for crappy typing