One of the uav projects I started last summer was a fixed blade coaxial rotor flyer that was steered by shifting battery weight in the style of the old Hiller Flying Platform . I put the project on hold while waiting for some lighter-weight brushless coaxial motors from Maxx Products (CR2805), and then got further sidetracked by the X3D-BL quad project.
This past week, I restarted the project, adding a mount for an SRV-1 Blackfin Camera board set, and writing the code to drive four servo channels - two channels for the E-flight electronic speed controllers, and two channels for the servos that gimbal the battery pack using a hobby helicopter swashplate. The servo interface is working quite well, and I have a slightly modified version of the java console used for the X3D which shifts the battery weight and controls the throttle. Horizontal translation is controlled by shifting the battery weight (as seen in the following videos), and yaw is controlled by trimming the difference in speed between the two prop motors.
In the first video, you can see how the weight shift mechanism works. However, I found that my battery pack was not producing sufficient output, so the flyer never got very far. In the second video, the battery had been replaced, but clearly some work is needed on steering. The crash at the end shortened one of the props by 0.5", but everything else was fine.
I think the basic structure is there, so the next step is to add accelerometers to aid in stabilizing attitude. I have both a 2-axis Analog Devices ADXL202E and a 3-axis LIS3LV, so I'll add one of the other. A gyro is clearly needed as well for yaw control, and I'm not yet certain which to use - I have a few with SPI interfaces that require 5V, or I might go with an analog output and use a voltage-to-frequency converter to capture the signal, since I don't have any A/D channels.