You can use EDTracker with the open-source Opentrack software, which itself can emulate FSX, TrackIR and FreeTrack protocols (amongst others). This opens up the 3DOF tracking to a plethora of games - anything that supports one of the protocols that Opentrack provides. To set up EDTracker with Opentrack, follow these steps...
Using the EDTracker configuration GUI, set the EDTracker to LINEAR mode and then turn the Yaw and Pitch scale values down to 1.0 You can adjust the ratio of physical-to-virtual head movement easily in the curves feature within Opentrack, so setting a high sensitivity here is not needed.
The auto-centering function within EDTracker can feel a bit weird when using it with Opentrack - some people prefer to turn it off, but this can cause problems with drift if you do not have a well-calibrated device. If you can afford it, the magnetometer-enabled MPU-9150 version of EDTracker is better suited for Opentrack use, as it does not rely on the auto-centering function needed for the MPU-6050 hardware (with no magnetometer).
The short answer is - try playing with and without auto-centering and see which you prefer!
Install & Run Opentrack
Download Opentrack from the releases link on the above GitHub project page, unpack it and run the opentrack.exe executable. The Opentrack GUI will pop up and should look similar to the below.
Choose "Joystick" for your main tracker, then click the Settings button and point Opentrack to your EDTracker device as the source for joystick input (remember - EDTracker just pretends to be a joystick, your PC doesn't know it's anything different!).
Choose Tracker Protocol
Opentrack supports many different tracker protocols - FSX, FreeTrack, TrackIR, FlightGear and can also push output via UDP to another Opentrack host. It can also drive output on a virtual joystick (vJoy) or emulate mouse look. You will select the protocol that best suits the game you are playing but, for now, we will use the FreeTrack protocol to provide output to games that support FreeTrack and TrackIR.
Select "FreeTrack 2.0" under the game protocol drop down.
Click the Settings button. In the pop-up dialogue box you can choose whether Opentrack will offer just a single protocol (FreeTrack or TrackIR), or both. Generally, both should work unless you find some sort of conflict and need to specify only one.
An important step is to set up the mapping curves; these translate the amount of input movement on your device (in this case, the EDTracker) with the amount of virtual head movement you see in game. There are no hard-and-fast settings to put in here as it will depend greatly on your preferences, how far away your screen is, how large your screen is and so forth.
Click within the top graph to place a point marker, then drag it to the top corner. This create a straight, linear translation.
By clicking elsewhere you can add additional points and build up a curve that suits your preferences. The process will be one of trial and error - you can tweak the settings while your game of choice is still running - so our best advice is to just play around with the curve settings until you find something you like.
Repeat the process for the Pitch and Roll tabs. There is no need to set up any lines for X, Y and Z as EDTracker does not provide those axes.
Finally, in the options tab, you can remap the input and output axes, should you find that yaw does not map to yaw, for example. You can also handily invert them here, should you need to. Note only the yaw, pitch and roll axes are of any use with EDTracker.
You can choose a "filter" that will process your tracking movement and reduce any 'noise' (unwanted small movements/jitter). It is optional, but can improve the experience. Try them out - generally the Accela Filter works well.
You can set up a keyboard shortcut - a "hotkey" - to re-centre the tracking. In the below example, pressing the HOME key will re-center your in-game view. This can be excellent for combating any yaw drift over extended periods, but should not be considered an alternative to avoiding calibrating your device! Magnetometer-enabled devices are unlikely to need the re-centre functionality.
You're done! Keep Opentrack running, and fire up your game in question - anything that supports one of the Opentrack protocols should recognise it and work. So anything with FreeTrack or TrackIR support, in the above example (Arma 3, Euro Truck Simulator, etc.).
Follow the instructions within your game for setting up your headlook controls. Generally this is game-specific, but at a summary level :
Analogue look-left/look-right operations should be bound to your TrackIR/FreeTrack left/right yaw options.
Up/down maps to pitch up/down
Roll, where supported, follows a similar process
Avoid mapping the translational axes by mistake - if you only have an EDTracker and no additional trackers, the lateral axes don't do anything.
You may need to flip axes if you find left looks right or up looks down - you can do this in Opentrack under the Mapping -> Options tab.
Massive thanks to Antmax off the ED Forums for working with the creator of Opentrack, Stanislaw, to get it working...