Before I get to the whole of what I want to say, I'd like to just make sure that there's a few things addressed: Firstly, I've been reading a variety of threads on how something of a sort akin to NerveGear could be developed in theory. While I understand that many individuals would try to advocate for the non-intrusive model depicted in the anime, I personally am one to support CraigD's proposal of using the nanotechnology. While people may speculate on the dangers of using such technology, I would like to point out that such a system, coupled with a backup battery (in the event of a power-outage), would in fact be better overall when considering safety. Unlike the microwaves used in the anime, which as we all know require a certain amount of power to be produced, the nanotech would ensure one's safe and immediate reentry into "real space" while avoiding potentially sending the user into a state of permanent paralysis. This then trumps any other ethical issues related to the invasive technique, as there is also the potential for the excessive radiation generated by the waves to damage tissue in ways that we have as of yet to detect and/or track for a sufficient amount of time. While I ain't a professional in Philosophy, I do happen to major in the subject. Secondly, the issue of overheating the system itself needs to be addressed. Currently, technology as it stands can only allow for certain amounts of run time of an operating system with the use of fans to circulate cooler air into the heat-generating system. Should there be insufficient coolage, the system will just shut down--as I'm certain we've all experienced at some point or other with our various other devices. Silicon, while versatile, has its limits. In another thread, the possibility for using diamond-semiconductors actually seems viable given that the anime actually references the use of such items within the system (http://swordartonline.wikia.com/wiki/NerveGear, "Transceivers"). These not only could potentially cut the overall heat generated by the system, but produce the speeds needed to run the game on a whole. Beyond all of that, I believe that there is huge potential with submitting proposals for grants to kickstart the development of these nanobots, as well as the threads and number of electrodes requisite for the project to move forward. The largest issue posed however is the human testing of such materials. As Internal Review Boards stand now, it would be a long an arduous process to get every test requisite for developing these items approved. Their biggest concerns, I think at least, would be of the nanobots detaching from the electrode-shafts within the human body and having no viable way to remove the shafts (which could potentially damage internal organs, but that's another series of events entirely). Going with the diamond-semiconductors, as well as matching the helmet to the individual to ensure the specs are perfect for the user, there's the potential to inlay speakers in every facet of the machine--albeit they would have to be very numerous to compensate for relative size. One might even go so far as to suggest that a screen be placed on the face of the device so that individuals could contact the individual in-game for efficiency's sake. The challenge would be to develop a cushioning for the helmet that is not only durable, but moldable and able to provide relative comfort, while also housing the nanobots and sheathes. As for how the game itself would run, it does show in the anime that a cartage is inserted into the device. This could potentially be circumvented by using what we consider a super computer in today's sense of technology. Those are just my thoughts.