With all the litigation over intrauterine devices, designing new contraceptives may seem a hazardous undertaking. But a Springfield, N.J., company is convinced people want a more convenient non-pill birth control.Yama is testing a barrier device for women called Lea's Kap, which can stay in place 72 hours. With encouraging trials at the University of Southern California and in Paris, the next step is a large-scale study. -- Leslie Brokaw