Addicting game,

Puzzle Bobble

Or the alternative Frozen Bubble:

http://www.frozen-bubble.org/

Its open source, so i don't really assume it should be that hard.
And its so fun. Cmon now.

Open source != Easy to port

Not the same thing by a long shot.

I will agree that the original puzzle bobble is highly addictive, and imo better than all of the web games apple is currently offering. Not sure what the chances of seeing this on the iphone are, though.
Would certainly be cool, esp. with multiplayer support!