It's a documentary inspired by Tweets from Tahrir, called Tweets from Tahrir! It airs on Al Jazeera English at 8pm in the UK, 10pm Cairo time. We saw it at a preview on Monday - it's a great film, actually moving in places, and funny at times too. It’s well worth watching, especially if you’ve read the book to put faces to Twitter handles.
In the UK Al Jazeera is channel 514 on Sky or 89 on Freeview. It’s also streamed live online here: http://www.aljazeera.com/
The film doesn’t just cover the 18 days but the year since (I did some extra research work for Al Jazeera). It has been masterfully put together by Adib Nessim.