What "stealth"? Even the article says Nantero has been working on this for over a decade. They and Lockheed had a NVRAM back in 2008. It was sent into space in 2009, along with a memory tester. It's radiation-hard, so it has space applications.

The technology seems to work fine. Manufacturing cost is apparently the problem. Nantero has been trying to fab the things in something close to a standard fab. They may eventually succeed at getting the cost down, but they've been struggling financially.