“I’ve been at finish lines where people come across looking like a hardware store,” said Andrew Graham, the chief executive of Bones in Motion, which makes the software Kaye will use in his Motorola Motokrzr K1m phone.

Technology is adding a new sound effect, beyond the roar of the crowd and pounding of feet, to many races. “In runs these days, it’s common to hear beep beeping,” said David Willey, editor in chief of Runner’s World, referring to the alarms on the heart-rate monitors worn by many runners to track their pulses. “That’s definitely something you didn’t hear 10 years ago.”

Serious runners once thought that music players had no place in races. But that hasn’t stopped technology-dependent marathoners. Willey estimates that at least one in five marathoners wear MP3 players as they race.

But MP3s are also being used in novel ways to improve technique. Ideally a runner, to be most efficient, should take short quick steps—about 180 a minute. Jenny Hadfield, a coach who lives in Chicago, advises her runners to download the tick tock of a metronome to their MP3s to stay in step. “As runners get fatigued, their turnover gets slow,” said Hadfield, author of Marathoning for Mortals. Hearing a minute of a metronome’s beat midrace can put competitors back on track.

And some of today’s pacers use GPS gadgets. For the first time this year, Garmin, a leading maker of GPS fitness products, sponsored a dozen marathons and provided hardware for the pacers. The devices, worn on runners’ wrists, track their elapsed distance, average per-mile pace and elevation.

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