Invisibility Cloak Possible?
According to National Geographic, making an object become invisible is now within the realm of possibility. Basically, light can be manipulated so that an object appears to have vanished.
If you've ever tried to grab a fish out of the water, then you can understand the basic principals of invisibility: the fish isn't where you thought it was (ie: your brain was tricked by the way the light was bent as it passed through the water &/or the bowl).
In the example below, you are "seeing" what's behind the man (please try to look past the simplicity of the experiment)
There are many obvious applications for such technology, with a focus on being stealthy. Some not-so-obvious applications essentially reverse the fundamentals of invisibility to create objects that stand out like a sore thumb. This could be used for such things as road reflectors to satellite beacons.
So the long and short of "invisibility" is this: even if no one ever creates the Holy Grail that is the Harry Potter Cloak of Invisibility, there will be other lucrative technologies invented along the way that will make the quest well worth the pursuit.