Mobile robots have been used for years by the military and law enforcement, but with falling costs, the next frontiers are the office, the hospital and the home. SACRAMENTO — Dr. Alan Shatzel’s pager beeped at 9 on a Saturday morning. Dr. Shatzel, a neurologist, hustled not to the emergency room where the patient lay — 260 miles away, in Bakersfield — but to a darkened room at a hospital here. He guided the roughly five-foot-tall machine, which has a large monitor as its “head,” into the patient’s room in Bakersfield. “Computers are beginning to grow wheels and roll around in the environment,” said Jeanne Dietsch, a veteran roboticist and co-founder of MobileRobots Inc ., a robot maker in Amherst, N.H., and a division of Adept Technologies.