I think the device which can detect the earthquake or detector.
transparent phone mobile...:) :)
they already have transparent mobile phones, its in taiwan
yeah.. your right i ddnt read clearly his question :) sorry...but im still thinkking
what about ..robot?.. haha sounds fun?
A device that you can download skills directly to your brain and you can become a spy, a professional parkour, a professional athlete, and much more. You can be whatever you want in just one download :)

advantage of this is like what i said, you can be almost anything you want to be.

disadvantage of this is, you might download something you might regret, so be careful what you download.