We heard that a possible way of doing it would be through the Microsoft Kinect.
After some research, we found that the best software for our needs was IPISoft's IPI Studio. This software has the possibility f using two Kinects to record front and side motion.
We did some initial tests using just one camera and had some very good results. It was also very simple to move them from the software into the UDK
We then organised to try two Kinect cameras.
Unfortunately, after setting up everything, we couldn't get the software to analyse the data from two cameras. It instead just used one, leaving half of the actors body behind...
We decided then to try to get a usable walk-cycle out of it using just one camera.
I will post the results later.