[Happydude]

a) Exists allready, just not to the public, i.e. only the US secret military, or NSA if you want to vcall it that, has them.
b) like GM said...allready exists, just not to a Huge scale...
c)Lightsabers are not posible, since light can not be stopped unless it is absorbed by something black. but then that wouldnt really look much like the light saber is supposed to. but theoretically it is posible to make one.
d)that i am not sure of...