Your PDA tells you many things—the time of a meeting, the phone number of a colleague. It entertains with games and MP3s. But it does not tell you to step right to avoid a landmine. It does not tell you to pull the trigger. Not unless you are a Marine, that is, and the device is the D-DACT, a PDA the military hopes will do nothing less than take war into the wireless age. Instead of drifting dangerously out of touch, soldiers will be networked through D-DACT modems, which communicate over military radio frequencies.