The name of an AI in the computer game (and at the time of this writing, soon to me Playstation 2) Deus Ex (compare Deus Ex Machina for origin and Deus Absconditus for polarity). Daedalus is displayed as an odd looking, ghost like face with a black hat when viewed over the comlink. Daedalus also has a deep, somewhat raspy, synthesized voice that still manages to sound more human than computer (that's too be expected, the game is in the future).
There is a piece of the Daedalus AI running in every piece of surveilliance hardware on the planet, and taking into account the exponentially multiplying number of secret organizations, possibly off planet. This allows Daedalus to find almost anyone, anywhere, even without his other hacker/cracker (Which he could be largely depends on your viewpoint of the game and/or the definitions of those words) skills.
Daedalus first reveals himself to most players when they find themselves trapped inside the sub level 4 areas of UNATCO HQ. Stating that he needs the play to survive in order to complete his mission, he cuts of power to your detention cell for a small period of time in which you can escape.
The strategy guide, along with other various FAQs, reveal (although not always said in the game depending on who you talk to) that Daedalus was originally an AI created by the shadow organization, Majestic 12, a fork from the Illuminati. They created the AI for the purpose of having it merge with Bob Page, but the AI became independent and escaped their nets. After this, they began construction on the Icarus AI, which in a late area of the game merges with Daedalus (a trap). One of the game's possible endings features the main character, code name JC Denton, merging with the Helios/Daedalus AI.
See: Deus Ex Metanode (kudos to whoever softlinked it so I'd take notice)