Air freight company DHL recently started using a real-time wireless locator device that can be affixed to boxes of mission-critical cargo shipped by medical and pharmaceutical companies, among others, that require urgent delivery around the globe.

The DHL Smart Sentry locator is the first such device to be certified by the Federal Aviation Administration for use on five commercial airlines, said Matt Groppe, DHL's director of global same-day sales.

"We hear our competitors are working on similar things, but we are glad to be first to market," Groppe said.

The device is about the size of two cigarette packs - 5 by 4 by 1 inch - and it's rechargeable. DHL's shipping customers can order the locators to affix to packages. Customers also will be able to recharge the devices through a USB port or a wall charger, Groppe said.

The device is not intended for one-time users, but for companies that have regularly ship for urgent materials, he said. For example, a bio-pharmaceutical company could use the device to monitor the location of an antidote sent in an emergency. Sensors in the device will also track changes in temperature, humidity, pressure, shock and vibration.

The device also knows to turn off automatically while on a flight to avoid interrupting airline communications, just as passengers on commercial flights must turn off their cell phones, Groppe said.

The device uses GPS and GSM radios. Communications on a package's location and other key criteria are sent to the DHL data center in Sterling, Va., and posted on a website for customers to monitor.

Shippers in many industries have asked for the monitoring and tracking capability, according to Groppe, who said the service will cost "several hundred dollars a month per device."

Customers that have asked for tracking capability include medical companies that need to ship sensitive cargo such as transplant organs. Technology companies have also expressed interest, saying they could use the device to send prototypes. Oil and gas companies would like to use the technology to monitor parts sent to field operations, and museums and movie studios could use it to make sure their goods are not exposed to light or vibration.

DHL spent about three years developing the device, which is manufactured by a third party that DHL didn't name. In several months of use in the field, DHL discovered that having the device report the status of a package every five minutes burned through its battery too quickly, so status reports were reduced to once an hour, Groppe said. The rechargeable battery is designed to last up to two weeks.

Finding ways to preserve battery life "was our biggest challenge," Groppe said. One lesson learned in the development process was that the battery could be shut off when a package is delivered to foreign customs office where it might sit for a couple of days. During that period, customers probably don't need constant updates, he noted.

Smart Sentry is valuable because it goes to the heart of what customers expect from a package delivery service, according to Groppe. "Customers don't want their money back if there's a problem with a package," he said. "They want it delivered on-time and in the desired condition."