St, Paul, Minn. ? Former Minnesota Vikings offensive lineman Korey Stringer is the only NFL player to die of heatstroke.

Four years after he collapsed during training camp, the Vikings are exploring the use of a “radio pill” that would allow trainers to monitor players’ body temperatures while they practice.

“We’ve been discussing it for months,” Vikings trainer Chuck Barta said Monday. “We’ve been looking at different information. We’re looking to see if we’ll use it this year.”

The system was developed by Palmetto, Fla.-based HQ Inc., and already is used by the Philadelphia Eagles and Jacksonville Jaguars.

“It’s been a good measuring tool for us to help prevent heat illness,” Jaguars head trainer Mike Ryan said. “Any time you’re in Florida in the summer, it’s always a concern.”

It gets hot in Mankato, too, and the Vikings open camp there July 29. It was 84 degrees with a heat index of 97 the morning Stringer collapsed during conditioning drills. He had a body temperature of 108.8.

Stringer was treated by a team of doctors for 14 hours before his organs shut down one by one and he died at Immanuel St. Joseph’s Hospital Aug. 1, 2001. Stringer was just 27. An autopsy determined he died of multiple organ failure because of heatstroke.

The new technology has gained notice in the wake of heat-related tragedies that have claimed the lives of Stringer as well as college and high school players over the past few years.

At the system’s heart are the pills, which contain a sensor and are ingested by the players and wirelessly transmit their core temperatures to a hand-held device.

“It basically has a crystal in it whose frequency is proportional to a temperature,” HQ Inc. President Bill Hicks said. “As the temperature increases, the frequency increases and vice versa.”

Hicks said food in the stomach area could affect the accuracy of the readings. Once it reaches the intestines, a process that can take several hours, the pill delivers a true core temperature.

“It can stay in the body for a couple of days and the pill itself can operate for nine days,” Hicks said. “But generally, in the case of football players, the food’s going to push through more quickly and therefore the pill’s going to probably push through more quickly. So, as a general rule, it’s a 24-hour, one-day pill.”

Each pill costs around $40, though HQ Inc. sales/marketing manager Susan Smith said the price tag varied according to volume and NFL teams paid closer to $30 a pill.

A base CorTemp system consists of temperature pills and generally two or three data recorders, priced at $2,500 apiece. The data recorders allow a trainer to read a player’s temperature with each recorder accepting up to 99 sensors.

For an additional $4,000, a team can purchase a PDA (Personal Digital Assistant), a hand-held computer that allows one trainer to centrally monitor all players while their individual core temperatures are being taken by assistants.

The technology has existed since the mid-1980s.

The Eagles have used the system for two seasons, the Jaguars for one. Smith said the company has been talking to the Vikings, Tennessee Titans and Carolina Panthers.