24 is a show I really loved on TV. Kiefer Sutherland played the role so well and while you really need to suspend your disbelief when watching it (why doesn't he eat, shower, go to the toilet, recover from gun wounds, the list goes on), it's still a great show.
News of the movie has been rumored for quite a while now, but it seems that Imagine Entertainment and Fox have gotten the project off the ground and started the clock on '24'. Kiefer Sutherland is the key to this working and they're working around him and shooting when he's available, in April next year.
Nothing is known about the movie, but 24 finished its TV stint with Jack going on the run from the Government [again]. I'm guessing something will happen that requires him to come out of hiding, but how they'll get the "24 hour" feeling into a 90 - 110 minute movie is going to be the bigger question.