If your looking at something complex then stepper motors are probably what your after (but a controller designed to take input from the motor would have to be found). You can always just use a motor everyones familiar with such as say, a bosch 750 (although something as small as an astroflight, if geared enough may provide the same torque) and you could stick a potentiometer on the end of the gearbox for feedback like Eds done on storm IIs weapon.

Two joints? I believe adam clarks robot wowot, used pneumatics on such an arm - http://www.dmachine.tv/wowot.htmlhttp://www.dmachine.tv/wowot.html