As an update, I did some preliminary joint torque calculations as follows:
Assume the fingers have 3 links, with dimensions 70mm, 50mm, and 30mm (this is approximately the size I want, although the 30mm link might be a bit longer to accommodate its motor/gearbox). I'm also restricting the joints to move in the range of
[pi/4, 0, 0] to [3*pi/4, pi/2, pi/2] radians.
I tried two maximum forces at the finger tip: 5N and 3N, and ran it through an optimization program to find the joint angles that could provide that force for which the torque would be a maximum.
Turns out that 5N would require a maximum joint torque of 0.75Nm (that's 106.2087 oz-in to anyone using that measure), and the 3N would require 0.45Nm, or 64oz-in, of torque as a maximum.
The other motors also supplied a torque, but they were all smaller than this maximum, and I want to design to the maximum constraint. Luckily, cheap motors from robotshop can provide this torque. They're a bit big, but that's not a big deal for now.
Once the prototype is done, I'll probably invest in higher torque motors, but for now it doesn't have to do much...