In the latest push toward what technoids tout as "smart cars," Gm's Cadillac Motor Car Div. is offering a communication systems that can help drivers find where they're going and contact police or emergency medical service if they're held up, hurt or stranded. Gm's Onstar system, which was developed by Electronic Data Systems Corp. and GM Hughes Electronics Corp., will be offered as a $1,000 option this fall on Seville, Eldorado and Deville. it includes a voice-activated phone that will automatically call for help if an air bag deploys. It will give the car's location to the 911 emergency system. Last year, Ford's Lincoln-Mercury Div. introduced a remote emergency system that can be activated at the push of a button.