Handheld Combat

Gao Yanhong strides out of his Shanghai flat and slides into a taxi. Opening his sample case, which is filled with designer shades, he grabs his wireless handheld computer and begins his morning routine: trading the mainland's volatile "B" shares online as the taxi weaves through traffic. For Gao, who sometimes slips out of sales meetings to check on a preprogrammed stock alert, the personal digital assistant (PDA) has become indispensable. "I always take my PDA with me," says Gao, whose specialty model, made by niche player GWcom, sells for $240 in a market where stripped-down devices go for as little...