It's called the PlayStation Portable Remaster Series, and sees certain PSP games re-released on the PS3 with enhancements like exclusive new content, HD graphics, control pad support, 3D visuals and more.
There's even multiplayer compatibility, with the PS3 versions of the game able to be played over Sony's Ad Hoc multiplayer service for the PSP.
This series will kick off with a revamped Monster Hunter Portable 3rd in Japan. Here is the first video of it in action:
I find this move rather odd, unless of course this all ties into the NGP (which I am sure will have a heavy presence within Sony's E3 keynote and booth). Personally, I feel revamping PSP titles in this way is a waste of time and money. Developers should be looking forward, not back.
Then again, Monster Hunter sells like crazy in Japan, and there's yet to be a true PS3 version so I'm sure there will be plenty of fans who will happily pick this up. At least you will be able to move your save game between the PSP and PS3, as well as play multiplayer ad hoc games.