My company does a lot of work for the US Department of Defense in this area. The biggest problem in that we face is that there are no standards yet. One vendor's tags can't be read by another vendor's interogators. So in order to set up an end-to-end supply chain system, DoD has had to stick with one company, Savi and his proprietary,expensive, and closed system.
Supply chain management within DoD would realize huge improvements with something like a universally readable active tag. With Microsoft and Wallmart into the action, hopefully, some standards will emerge