I've been looking for something similar and have been combing the forums. There is a US company that makes a dual camera adapter, Brandmotion 9002-2781, that would allow you to add a front camera. Its a bit pricey, ~$300, and you still need to buy a camera, but the image will come up on your...
I know its been awhile for this thread, but a company called Brandmotion makes a dual camera adapter (kit 9002-2781) that would allow you to add another camera such as one for the front. Its a bit pricey @ ~$300 just for the adapter so I haven't pulled the trigger yet, but thinking about it.