A remote controlled toy
The remote controlled toy was a toy controlled by a remote used by children in the 24th century.
Alexander Rozhenko was playing with the toy when Jean-Luc Picard, who was temporarily turned into a child, asked to borrow it. It was used in the successful retaking of the USS Enterprise-D from a group of Ferengi in 2369. (TNG: "Rascals")
Background
This object was simply referred to as a "toy" in the episode and in the script. The script described it as a "cross between a lunch-box and a spider [with] no apparent wheels."
The prop was put up for auction in the It's A Wrap! sale and auction. According to the auction, the bottom of the toy features hangars which allows it to be hung up on a wall.