Pocket Pikachu, known as Pokémon Pikachu outside of Japan, "is a step counter and virtual pet toy in which the player looks after a virtual pet Pikachu... The unit is strapped onto a belt and used as a pedometer. Every 20 steps the unit registers give the user 1 watt, which is a currency that can be used to gamble or buy Pikachu presents." 
The original unit launched in Japan on March 27, 1998 and in North America on November 2, 1998. It is a small yellow handheld with a black-and-white LCD, D-pad, and 4 buttons.
A later version, "Pocket Pikachu Color: With Gold & Silver!", known as Pokémon Pikachu 2 GS in North America and Pokémon Pikachu Color in Europe, was released in Japan on November 21, 1999 and in North America on October 16, 2000.