Attemps to improve airport security with new technology have led to tools for identifying people using iris scans, handprints and even cellphones to track movements of passengers and airport personnel. Some innovations also promise customer-service improvements, such as notifying passengers of changes in departure times or gates by cellphone or pager instead of an unintelligible public address speaker. At Billund Airport, Denmark's second busiest gateway, a wireless network was tested for several weeks in February using a voluntary database containing passengers' names, addresses, passport numbers and mobile telephone numbers. Large blue tags that passengers either carried or attached to their carry-on luggage and then surrendered at boarding allowed them to be tracked by airport security. The system, developed by Red-M, a British company, and BlueTags of Denmark, uses Bluetooth computing technology to track sensors. It allows security personnel to see if a tagged bag is somewhere suspicious or if someone entered the wrong terminal or gate, said Laura Cleveland, a Red-M spokeswoman.