In Iran recently illegal protests were aided by such things as cell phones, Twitter, etc. However, such mechanisms can be fairly easily thwarted. If a group wanted to overthrow a repressive government, it would need to construct an unbreakable communication apparatus for planning and implementation. I would think that such an apparatus could be designed and run "open source" so even if the government in question attempted to interrupt it, they couldn’t. How would you go about constructing such an apparatus?