Enter the Motorola Lapdock
I bought one of these several months ago for my Atrix 4G phone when a clearance website had them for $60. This dock has a male Micro-HDMI port and male Micro-USB port on it to interface to the Atrix phone. I thought this would be a great interface to use with the Raspberry PI; the only pain was finding the right cables/adapters.
I knew I had to go from those ports to a full size male HDMI, full size male USB and micro USB for power. Getting the cables needed cheap was a bit of a pain; but eBay and China sellers came through.
Now that I had all the adapters I needed it was time to build the cable.
Cables Hacked Apart
So I took two USB cables I had lying around and cut them apart. One of the USB ports would be going to the Female Micro-USB to Female USB adapter I had bought. The other would be going to the Raspberry Pi's USB ports. The Male Micro-USB cable portion would be hooked up to the power port on the Raspberry PI.
Rough Fit of the Cables
The next step was wiring it all up, ensuring the only the power lines went to the Micro-USB adapter and the D+ and D- lines went to the other USB port on the Pi.
Starting to Solder up the Harness
Now since I have a harness with two of the same type of USB ports I wanted to label to make sure it didn't ever get hooked up wrong.
Harness Labeled Soldered and Taped Up.
Now as I stated earlier I needed a couple adapters that I bought of eBay to hook up. to the Pi. For the HDMI I got a Female Micro-HDMI to Male Micro-HDMI cable and a Female Micro-HDMI to Male HDMI adapter.
All that was left to do was hook it up to the Lapdock
Harness/Adapter Cables Hooked up to Dock/Pi
And Power it up
Powered up and Connected
So now I have a nice portable Monitor/Keyboard/Mouse/Power Supply I can use with the Raspberry Pi.
Now all I need is a compatable WIFI USB Dongle and I will be truly portable!