Crypto carries the unit around with him. Whenever Pox is seen on it, only his head and cranial cords are visible. The Holopox Unit has three metal beams spining around it as it floats.
During the events of Destroy All Humans! 2, Pox downloads his subconsciousness into the Holopox Unit moments before the Furon Mothership is destroyed, allowing him to survive in a ghost form. It is suggested in the final cutscene of the game that the Holopox unit also contains a ghost version of the Furon Mothership's laboratory.
In Destroy All Humans! Path of the Furon, Pox has upgraded the unit to remove the spinning beams and to allow for arms.