Its on PSP and its called liberty city stories.
The main character is Toni Cipriani from GTA3, and it takes place 3 years before the events of GTA3.
You can't swim or eat or get skills and shit like in SA.
But there is new additions to the city, new weapons, new cars, a new weather effect (snow)..
I'll buy it. People are haviung a cry cos you cant swim, but they seem to forget its for a portable system... its fucking amazing.
Here is the site with all the info and screenshots:
www.gtapsp.com