Here is an article discussing in-memory tokenization vs. encryption:
http://www.protegrity.com/2011/06/memory-tokenization-replace-encryption/
Here is some info about the solution:http://www.protegrity.com/wp-content/uploads/2011/04/Protegrity-Tokenization-Whitepaper-3_2011.pdf
So far it looks like single company innovative solution but not a trend.