HTC announced in North America yesterday the release of the official Motion Tracker and the Vive Deluxe Audio Strap for the HTC Vive.
Both of them will be available for 99.99 USD (with tax) and the developers can get them from March 27, 2017 while the others can pre-order it from May 2, 2017 in the USA.

The details about the devices can be found in the official press release: