Do you need to know individual wheel torques? If not, measuring axle housing position could give you general torque, or engine/transaxle position on front wheel drive. I have seen something similar on older helicopter engines. Kind of crude, but may be what you need? Pay heed to previous response when considering this option. Does it need to work in snow or other types of sticky stuff? Are you really concerned with actual torque, or accel/decel of the wheel in question?