Cloaking devices
Meta materials have been in the news recently in regards to cloaking. Now some more active cloaking technology is being reported
active cloaking technique,science daily
Imagining a perfect active cloaking device, it would detect all incoming radiation while not reflecting any of it. Then it would broadcast all radiation as if it had passed through empty space. So, basically all the radiation that would be absorbed on one side of itself would be rebroadcast on the other side. It is an interesting problem and clearly significant advances are being made contemporaneously.