As a former platoon leader and S2(Viet Nam), as well as a computer nut who built his first one, rd909 and dpa are both correct: tactical action is too fast for this type of input to be useful. At best it is an annoying distraction, and at worst it is actively misleading. Please read the after-action reports from the Afghanistan FUBAR for the latter. Transmission rates and security would have to be several orders of magnitude faster and better for such devices to even have a chance.
Additionally, reliance on technology in tactical situations has been almost universally disastrous from a security viewpoint: check with the Germans on their experiences with ULTRA, for example. If you can send it, I can read it and mess with it. If I were going to go to war with a high-tech power, I’d use their technological reliance against them.
Finally, infantry combat was, is and forever will be a small-scale, brutal, personal, real-time activity; troops fire: fire-team leaders direct fire: squad leaders direct fire-team leaders: platoon leaders direct squad leaders, and platoon sergeants keep platoon leaders alive. Input from anyone higher is usually counter-productive. In contact, everyone else needs to send ammo and butt the hell out.