Opentrack was created by sf-editor as an open-source project based on the freeware Nuxe edition of Virtual Desktop. Free version comes with limited features. For more extensive features, an upgrade to the Pro version is required. The application is available for free download from subeditor's website.
In addition to recording your movements with the device, you will need a web camera to upload the captured data into the VR application. A special type of lenses will be needed for this task. You can also choose to use the SFP modules found on many SFP cards to eliminate additional hardware requirements. SFP cards are inexpensive and widely available. save money but will also be able to take advantage of upgrades that become available down the road. If you have not already purchased a Opentrack device, I would urge you to do so. You won't regret it.