The U.S. Army is replacing dog tags with smart tags ( memory chips). These "smart dog tags" would contain all the health related information about the soldiers. The final version of the new dog tag would be the size of a credit card. There are currently some 13,000 troops carrying a bulkier prototype.
Dog tags are a 20th century development, and by World War II, they were carrying a very vital bit of medical information, the soldiers blood type. Transfuse a wounded soldier with the wrong type blood, and you kill him. The "smart dog tags" would replace the existing ones (made out of stamped metal), when they became rugged and reliable enough to do so. By then, in 5-10 years, combat medics would use a small, PDA size, device to read the smart dog tags, by just holding the scanner near wounded soldier. As the soldier is treated, the smart dog tag would get updated. Thus the soldier would always have his complete medical history with him. That data would include allergies (especially to some medicines) and previous treatments.
The army has computerized medical information on 9.2 million troops and their dependents. The thousands of medics in Iraq and Afghanistan have PDAs that can access that data as needed. Quick access to this data is one of the many factors that has brought down the death rate in the combat zone. Having all that data in an electronic database also makes it much easier to find useful patterns in treatments, injuries and diseases. This, in turn, makes it easier to find and fix problems.