According to an article in BusinessWeek online:
The U.S. is moving closer to requiring citizens to have an identity card that could be scanned from a distance. By the end of 2005, U.S. passports will come with embedded radio-tag chips — and Congress is considering mandating similar technology in driver’s licenses. The government argues that the changes will make America safer from terrorists. But privacy advocates are appalled, fearing that the information could be stolen and misused.
Apparently, this would be done using RFID (Radio Frequency Identification), an electronic identification system which transfers data between a movable item and a reader to identify, track or locate that item.
Source: Ernie the Attorney