Nintendo has been granted a patent that was filed in 2001 for a gaming phone.
From the patent it appears that the phone will run two chips, one for games and one for other mobile functions. The official description is an “Electronic apparatus having game and telephone functions” but its clear that the main aim is games on a cell phone.
An electronic apparatus includes a phone CPU and a game CPU. When a * key is operated during execution of a game, the phone CPU sets a specified bit of a game key register to “1”. The phone CPU is set “1” into the specified bit when there is an incoming call of a phone during the execution of the game. The game CPU pauses the game being in execution when the specified bit is renewed to “1” and restores the specified bit from “1” to “0”. When the * key is operated in a state the game is interrupted, the phone CPU sets “1” into the specified bit. The game CPU restarts the game by canceling the pause.