Think about it, many cell phones are now lining up with GPS navigation in them, along with instant messaging programs, (universal ones such as Agile Mobile) and the increasingly popular picture-mail features that could be of use for silently coordinating attacks or something.
The GPS, well, guess it could be handy if the war is taking place throughout several streets in the hands of someone with no sense of direction. Text messaging is obviously quiet and a pretty good way to communicate to teammates, and combine that with picture mail--take a picture of the postitions of opponents guarding the flag if you're playing capture the flag, and send it to teammates (a picture is worth a thousand words, right?)
With all these nerf guns out there with the "rails" on top, it actually could be pretty easy to mount cell phones onto the guns. Of course, you obviously need a large "arena" to make it even worth the trouble, I actually sort of did this, but it was at night, and unfortunately...with super soakers (not an event hosted by me, otherwise it would have been nerf, soakers have no freaking range), it was roughly 35 vs. 35, (huge youth group event, and tons of guests) capture the flag and about 1/3 square mile, huge, buildings in between (college campus), trees, gazebos, lines of bushes, etc. It was probably the only good super soaker fight I've had, would have been an amazing nerf war (but nobody listens to genius). But any ways, me and several teammates broke off and got a lot of use out of our cell phones (wrapped in plastic for water protection), and we won 3 out of 3, long wars, over an hour each. As said before though, cell phones are only useful in large areas for wars (guess my new name is Captain Obvious).
maybe, txting can take a long time, sending pics and vids eats memory, and i wouldn;t want to strap my 300$ phone to a nerf gun. Nice thought, but for now im sticking with walkie talkies