Invisibility cloak! A reality ???

Lots of countries have been working on 'invisibility' technology for a very long time. I recall one Russian company in the early 90s publically announcing their intention to sell visible stealth technology that they said could be retrofitted to any existing aircraft (and they even called it a 'cloaking device'!). They were subsequently stomped into the ground by the Russian Air Force, so there may well have been something to it.

I'd just use a normal trip sensor alarm - if this technology actually works, and it can bend light and other parts of the spectrum, it still won't be able to return them to their exact original path unless you're wearing a perfect, solid cylinder around you. It'll be something more like the (surprisingly-visible) suit from the 'Predator' movie.

And I still don't get how they'll see where they're going. Unless they have some way to "unshield" their eyes, they'll be completely blind. (And, if I was on guard duty somewhere, and saw a pair of disembodied eyes float past me, I'd probably shoot first and ask questions later!)

I wouldn't worry about it. Human ingenuity isn't confined to any one nation. Whenever one group of flag-waving humans devises some new perceived advantage over their enemies, an opposing group of flag-waving humans ALWAYS finds a way to counter it.

And, usually, solutions don't even need to be sophisticated. For example, when they discovered US naval vessels can track/intercept X number of incoming missiles, the Russians said, "No problem... we can just launch X+10 missiles and sink them in one volley"... unless it was a carrier, in which case, they planned to simply nuke them.

And you don't even need to look at that level of conflict either: just look at Afghanistan, where you have most of the world's major military powers, with all the great gadgets and gizmos they can muster, and a decade later, their enemy—little more than farmers wielding AK-47s and home-made bombs—are STILL a credible threat.