There are loads of calculators available (PokerStove is just one of them) that can tell you the odds in seconds if you know what the players hole cards are.
TV commentators don't even need the answer in seconds though - their commentary is almost always recorded long after the game is over, so they've got all the time in the world to work out the correct numbers.
FWIW, the percentages announced on TV don't always take into account all the information they have. I think the PPT was about the only show to take dead cards (ie: cards other players had folded, which they'd seen via the pocket cam) into account - pretty much everything else ignores them.