Mini-Munchman was a handheld version of Munchman.
It was first produced in 1981 and also incorporated a watch, stop-watch, lap-timer, day/date & alarm.
The object of the game was to move around the maze eating pieces of fruit while avoiding ghosts.
Mini-Munchman was powered by 2 LR44 button batteries.
There is an article on Wikipedia relating to Mini-Munchman.