From Sonic Retro
Like Tails himself, but smaller, shinier, and not so scared of lightning, the remote robot is a remote-controlled exploration device, able to sneak into tiny passages which Tails is too big to fit inside. In this way, it is an integral part of solving many of the platforming puzzles which crop up amidst Tails' one-fox guerrilla war on Cocoa Island. The Remote Robot can activate switches, push rocks, and collect items in places his controller can't get to.
The Remote Robot can jump (by pushing ), and can hover for an indefinite period of time using helicopter rotors. Pushing cancels the remote control and warps the little robot back to Tails. While controlling the robot, the fox cannot be harmed by any Battle Kukkus that happen upon him. The Remote Robot is almost undamageable, happily capable of strolling over spikes and lava and right through enemies - but in the very last level, Battle Fortress 2, there are Kukku signal generators which interfere with Tails' remote control. If the Robot walks into their projections, it is forcibly returned to Tails.
In a marvel of robotic miniaturization, after Polly Mountain 1 it is revealed that the Remote Robot can transform into the Sea Fox, Tails' one-person submarine from Sonic Triple Trouble. The Sea Fox allows Tails to access the Lake Rocky, Lake Crystal, and Battle Fortress 1 areas.
In the end sequence of Tails Adventures, the fox is shown going through the arduous process of building a new, larger version of the Remote Robot - which blows up right at the finish, covering Tails and a nearby Flicky in soot.