AS much as Paul Hardin wants you to buy his products, he hopes you never have to use them. That’s because more than half of the people who do turn on his outdoor rescue devices “are at the point of death,” he said, and are otherwise out of options.

The products, called personal locator beacons, “are really devices of last resort,” said Mr. Hardin, vice president for sales and marketing for A.C.R. Electronics, a leading manufacturer of the beacons, which give lost hikers or stranded climbers a way to alert search-and-rescue teams at the push of a button.

After years of being used by private pilots and boaters, the beacons were approved by the Federal Communications Commission for use on land in 2003. But until recently, they have not sold well. The recent spike in demand followed two fatal headline-making events in Oregon last year: the deaths of three climbers on Mount Hood and the death of James Kim, who left his stranded family in the frigid, rugged mountains of southern Oregon to seek help on foot.

Even with the increased demand, there were only 18,006 of the devices registered in the United States at the end of last year, according to the National Oceanic and Atmospheric Association, which administers the rescue program.