Hi all,
I've been experimenting to get this working for a few days now and thought I'd report my findings. Obviously a lot of the information out there (from late 2014 / early 2015) is already out dated. There's a lot of now defunct information to wade through, a lot of dead ends but also some critical information amongst the pages of issues and attempts by everyone. I've tried pretty much everything - Opentrack / FreetrackNoIR / SweetFX + Re-shade / FreePIE / Trinus VR / Moonlight (previously known as limelight) / nVidia GameSTREAM / 2x Headsets / 2x Phones (Nexus 5 / One Plus X). I had the game working with FacetrackNoIR (not in VR) using a Microsoft VX-5000 webcam, but even tweaking the set-up curves (and trying a few posted here) the movement was too erratic to be useful in real games (although the system did generally
work. Using a gyro from the phone is the way to go for the best experience, unfortunately I've really struggled to get it working. A feel between the gap of ED going to 64bit and Trinus VR not having updated to support tracking natively it seems (see ayhinger's notes above for the solution, and links for files below)
My system for reference:
Windows 10 Pro 64bit
GTX 970
Haswell i5 @ 4.3Ghz
TP-Link Archer VR900 (reasonably well spec'd router with dual band and good throughput)
Nexus 5
My set-up is as follows:
Nexus 5 < Wi-fi <
Router > LAN cable > PC
Through trial and error here's where I'm at:
What you need:
Trinus VR - Combined app for streaming video and making head tracking input work in-game. Download app from Google Play and Windows 10 version online. App is £5 off GooglePlay
Moonlight - Free open-source app to allow streaming using nVidia's gameSTREAM technology. You can stream with other adapters built into Trinus VR, but I wouldn't recommend it, this provides good quality video and low latency.
SweetFX + Re-shade. See astearon's post #288 for links, or use my zip (see Downloads section) This corrects the warping distortion by using Elite's built in Side-by-side option in the graphics menu. No need for hacked custom resolutions if you use this (and I suspect better performance as a result?!)
Geforce experience
Steam (with Elite installed via Steam). There are hacks, but moonlight doesn't currently pickup non-steam copies of Elite as an option to stream at present.
Once you have Trinus VR running on your phone and PC, and you've opened the required ports. I recommend switching to Advanced mode for a cleaner interface (sorry loxai your "basic" mode UI is really bad

). To do this click the 'cogs' symbol and go to "advanced mode" from the menu.
Here's some screenshots of my settings for reference:
https://drive.google.com/file/d/0B1KboO68PzH3Wkw4OEVSTG1FWkE/view?usp=sharing
https://drive.google.com/file/d/0B1KboO68PzH3RWQtODlpM2ZZYVE/view?usp=sharing
https://drive.google.com/file/d/0B1KboO68PzH3Zm1JTDMzVWQ4dVE/view?usp=sharing
https://drive.google.com/file/d/0B1KboO68PzH3UEl3M3N3UFBiamc/view?usp=sharing
Main points are
Capture Mode: Moonlight
Sensor Output: Freetrack
Rotation sensitivity values around 25-30% (under 'sensor' tab)
Assign reset key to centre your view should drift occur (I have Num lock Enter for easy locating when the HMD is on and you're locating by touch only!)
Step-by-step
1) Install all programs and files - nvidia geforce experience (PC) / moonlight (phone app) / Trinus VR (both PC and app) / Apply Trinus DLL patch / Sweet FX files to Elite installer folder
2) Open moonlight app on your phone. A list of all compatible devices on the same network will be displayed so you can select one to pair with. Choose your main PC and a pop-up box will appear on your PC with a PIN code on your phone to enter. Do this and your devices will be paired. You can now exit moonlight app.
3) Open Trinus VR on both PC and phone. Check ports and IP address are open / match, set-up and per my screenshots, and press the triangle symbol to connect. Recommend doing to on your phone, then the PC. If all is well moonlight should start up (grey screen showing symbol for your main PC). click on that, then a list of all stream-able games will be shown, along with a Steam icon. Click on the steam icon and Big Picture mode will launch on your phone and PC simultaneously. Now you can browse to your Elite install and launch (you will be prompted for Elite or "VR mode" when launching, all I can tell it that it bypasses the launcher when selecting VR mode, so do that (saves a button click

)
4) If you've imported the 64bit DLL I'd listed below Freetrack (head tracking) should work once you're in-game (not at menus obviously) automatically, when moving your phone. Hopefully the video quality is usable. I use 1080p in-game and have moonlight stream at 1080p 60fps in the app settings (requires stable 20Mbps data-rate for default quality settings)
Notes:
* This only works for nvidia GPU's. I believe there's an ATI alternative but I haven't researched it
* You'll need to download Geforce Experience, open up and go to "Shield" tab to set-up and account with them so you can login to use the gameSTREAM functionality that the open-source 'moonlight' app utilities (it's free and takes only a minute)
* Make sure Elite is running no higher than the resolution of your phone display
* Set side-by-side mode in Elite graphic options
* If you have a powerful enough GPU (GTX 970 or higher) set AA to FXAA and Supersampling to 1.5 in Elite's graphics options for improved text legibility
* Enable V-sync to 60Mhz (might be unnecessary, but I do)
* Make sure the ports listed in Trinus VR for the Sensors and Video input (under 'Network' tab) as open in your Windows firewall
* Ensure Phone & PC are connected to the same network so they can connect (same router via ethernet or wifi)
* Ensure IP address on Trinus VR PC GUI (in 'Network' tab) matches the one shown on the App screen (this is the IP of your PC for reference)
* No need to enable USB tethering for this method as some of the videos show, my tests found it to be flaky and wifi providing sufficient bandwidth and low latency using moonlight/gamestream (nvidia GPU's only). Results will depend on your router speeds.
* See vayhinger's post above. Trinus VR doesn't ship with necessary 64bit dll for Freetrack to work with Elite at the time of writing (so my testing would indicate). You need to download them (see my link below) and insert them into the "ext" folder inside the Trinus VR install dir (along with 2 existing non-64 bit versions already present with the same names for reference). These files were acquired from an install of FacetrackNoIR, so you can skip having to get them yourself
Even with all that I still experience the rapid flashing on a static cockpit image between (working) head tracking images as Al33 describes in post #290. For reference if you focus on a cockpit menu the flickering immediately stops but returns when you centre the view again 
Hopefully this can be solved as otherwise the experience seems to be working in all areas (video quality / tracking accurancy / latency).
Downloads:
SweetFX (see readme inside zip)
https://drive.google.com/file/d/0B1KboO68PzH3bHRkeFR2S1d5OTA/view?usp=sharing
Trinus VR - Freetrack 64bit DLL's (install to ...Trinus VR / ext / *here*)
https://drive.google.com/file/d/0B1KboO68PzH3cWhqRzcyYlpUQlE/view?usp=sharing