I don't know whether a replay is a good course of action. The way football is judged is through the referee and the linesmen; sadly video evidence is not allowed, as with other sports - presumably due to "tradition" (I can't think of any other sport that's filmed from as many angles as football, so the infrastructure is there). The action is described in the Huffington Post as:
The game appeared headed to penalty kicks when Florent Malouda sent a free kick to Henry at the post to the right of goalkeeper Shay Given in the 103rd minute. Henry got between defender Paul McShane and Given, stopped the ball with his left hand, then used his hand again and poked the ball with his outstretched right foot in front of the net.
"He almost caught it and walked into the net with it," said Robbie Keane, who had put the Irish ahead in the 33rd minute.
Gallas headed the ball into the net from about 1 yard as Irish players raised their hands in protest at Hansson.
From: Thierry Henry Handball Goal VIDEO: "Le Hand Of God" Goal Puts France Past Ireland
Clearly the problem is in the way the game is reffed. It's very noble of Blackmail! to accept an injustice has been done - fair play - but the same could be said of scores of games played across Europe, all of which cannot be replayed.
The French should enjoy the win; after all, a bit of controversy is part of the game.
But hats of to the French; looks like Henry's been in England too long.
Edit: This bunch don't seem to have the same sporting attitude as our French chums:
BBC News - Egypt recalls Algerian envoy as football row deepens