Mike Marr: The robotic companion is a Hodgsons Robotics Unit Mark V, or HR-V for short - it's usually pronounced "Harvey" - that serves as Seth's sidekick for most of game, and can be used in a variety of configurations. It can be customized with different weapons, ranging from a devastating long-range sniper rifle to a napalm shotgun. You can also tailor its abilities, and whether it's more of a tank or a damage dealer.
HR-V auto-targets based on threat level, but you can issue it specific attack commands, tell it to move to specific locations, and control the use of its special abilities.
An interesting note is that it has "issues" with the maintenance robots on the ship.