The Liam Neeson character in Fallout 3 isn't just a "for hire" gig because the character in the game was actually written with the actor in mind and, according to Reuters, provides the dramatic foundation for the entire Fallout 3 experience. source
Fallout 3, in development by Bethesda (Elder The Scrolls IV: Oblivion), is an RPG set in a post-apocalyptic Washington D.C. (from what I've been able to gather). There is no word yet on a release date or what systems the game will play on.
The official site does say that a trailer is due in 27 days. I'll update you when that time comes around.