In case anyone has one lying around and wants to see it in action, you would want the following accessories:
1. USB-C to HDMI adapter ( I opted for 1 with HDMI, USB 3.0 & USB-C in for power )
2. micro HDMI to HDMI cable
3. Female micro HDMI to Female micro HDMI adapter
1. Modified USB A to micro USB cable ( more on this later )
2. Female micro USB to Female micro USB adapter
3. USB Cable + Charger to charge your phone
If all you want is to bring up dex on your lapdock, all you need are the HDMI connectors. You will want to use a Bluetooth keyboard & mouse to navigate dex and will not be able to charge your phone.
Going 1 step further, you can use a multi-function USB-C adapter with HDMI, USB OTG & USB in for power.
Here, you would modify a usb cable to give you access to the lapdock keyboard & mousepad. The lapdock was designed to be an all-in-one setup with the Atrix phone, so the 10 hour battery could also charge the Atrix. <-- That's our problem. So you will need to snip the RED wire in the usb cable to prevent the lapdock from potentially frying your phone or other devices.
Theoretically, you can charge the phone using the 2 usb ports on the back of the lapdock, but it's a trickle effect. It'll take forever and you won't be happy. I did it in a pinch & running any applications under dex still consumed my phone's battery. Plugging it into a charger, though, kept my phone @ 100%.
A big caveat here is the mousepad is NOT multitouch, so I still used my bluetooth mouse for the scroll wheel.
Here's where this becomes a lot of fun... the lapdock screen is great for running emulators in a decent window. I plugged in my shield gamepad with a usb cable into the back of my lapdock and was able to play pretty much anything I wanted to. Still plugged into an outlet kept the phone @ 100% while emulating 100%+ speeds.
The larger screen is also very nice for streaming tv/movies.
There is an option in the Dex control panel to output audio through the HDMI cable, so you aren't relying on your phone for audio.
Anyway, if you have one of these gems lying around, it's a great way to extend the value of this phone.