Automation and Control Technology (ACT) is aggressively marketing the Advanced Photonix (API) T-Gauge

My Note:  Automation and Control Technology (ACT), appears now to be aggressively marketing the Advanced Photonix, (API), T-Gauge as part of ACT's new Envision M-Series.
http://www.autocontroltech.com/mseries/video.html
http://www.plasticsnews.com/article/20120829/NEWS/308299954/act-integrates-t-gauge-on-measurement-equipment

The ACT webpage has several pages and links to THz related news:

To minimize raw material waste and improve product consistency, manufacturers of multi-layer non-ferous products now have a cost effective alternative in a single-sided Terahertz sensor from ACT. Traditional Nucleonic and X-Ray transmission or backscatter gauges, use radioactive sources and their use requires compliance with government regulations. However, the Terahertz sensor is a safe non-nucleonic device. The time domain terahertz pulsed source allows the simultaneous measurement of each layer: thickness, basis weight and moisture levels in extruded or cast multi-layer sheet products. Terahertz sensors are more accurate, safer and economical.

For more information Click here http://www.autocontroltech.com/newstwoA.htm

In addition, there are scholarly papers, such as the following one by David Pond, explaining why  time-domain terahertz is particularly well-suited to industrial process control:

http://files.eventsential.org/61198b3c-1544-484a-a2b1-01ec6810ec04/event-94/36018929-Pond-David_-paper-15-06-2014.pdf