![Image](http://i.imgur.com/Pxptul.jpg)
The Adjacent Reality Tracker has 3 axis each of accelerometer, magnetometer, and gyroscope, an RGB LED, an 850nm infrared LED, a lithium ion battery and onboard charger, a USB interfaced microcontroller, and a Nordic radio transceiver. The bare Tracker is around 1.1"x1.1"x0.3" and weighs 9.2 grams. I'll be 3D printing enclosures for these prototypes, but I'm looking into injection molding for the future. While I haven't done full battery life tests yet, the expected usage is on the order of 8 hours. Parts cost for the Tracker in prototyping quantities (100) is around $30, and around $12 for the Base Station.
While the on board microcontroller is capable of doing AHRS sensor fusion and outputting a quaternion at roughly 120Hz, it can more usefully and quickly stream sensor data to a host computer to be processed there. The gyro is capable of sampling rates up to 760Hz, and the Nordic link has the throughput to transmit that fully with under 1 ms latency to the Base Station. (USB will be the long pole for latency)
The Base Station USB stick can interface to up to 6 Trackers, but due to on air collisions at high data rates, 3 is probably the practical limit for real time virtual reality applications. The Base Station exposes any available Trackers to the host computer using the new USB HID Sensor descriptors. The Tracker can also be interfaced to a computer directly via its micro USB connector, where it also appears as a collection of HID Sensors.
The hardware design is approaching complete, now that I have ditched Bluetooth for latency/jitter reasons, but the software is still under heavy development. You can see it in action at GitHub. The software is currently under the GPL, but will be BSD once I remove sensor fusion from the firmware. The hardware design is Creative Commons.
The plan at the moment is to complete the software for this board revision. I only just finished assembling the first couple of boards today, but once I have more done and the software in more complete form, I'll be sending them out to people willing to help with development of the firmware, host interface libraries, or applications. The longer term plan is to launch a Kickstarter towards the end of the year if there is interest. I'll be pricing it as close to break even as possible.