"Imagine a world," said cardiologist Leslie Saxon, "where you turn on your computer and, along with surfing the Web and turning on YouTube, you can check your or your family members' health stats."

Saxon was opening the first annual Body Computing Conference, at the University of Southern California, in Los Angeles, on October 26. She offered a definition of body computing: implanted wireless devices that transmit real-time data about the body to doctors, patients, and relatives.

The prospect of such devices interests some of the biggest health-care companies in the country. Panelists included the CEOs of Boston Scientific and GE Healthcare, and high-level executives from Medtronic, St. Jude, Texas Instruments, and Johnson & Johnson.

The conference hall was packed with scientists, engineers, physicians, and venture capitalists.

The heart is a big target of body computing. Several of the panelists, including Jim Tobin of Boston Scientific, discussed implantable heart defibrillators (more technically called implantable cardioverter-defibrillators, or ICDs) that store a continuous record of heart activity that can be analyzed by a cardiologist. (See "Defibrillation's Alternative.")

Other kinds of devices were discussed as well. Garry Neil of Johnson & Johnson talked about miniature, pill-shaped cameras called PillCams that can take thousands of photographs of the inside of the intestine and transmit them to a waist-worn receiver for later downloading. (See "Swallowable Sensors.")

Chris O'Connell of Medtronic discussed devices for diabetics that measure blood-sugar levels hundreds of times a day, revealing trends that may be missed by traditional finger-stick methods. And startup companies, such as MedApps of Scottsdale, AZ, are aiming to perfect systems that wirelessly monitor blood-sugar levels and send the data to physicians via the patients' cell phones. (See "Your Daily Digital Doctor.")

One panel was moderated by Andrew Thompson, the CEO of Proteus Biomedical, a startup based in Redwood City, CA. Since he was the moderator, he didn't talk about his company, but a magazine article distributed at the conference ("Proteus Biomedical: Using Computers to Manage Chronic Diseases," In Vivo, March 2007) describes its goal of creating a "smart pharmaceuticals" system in which computer chips embedded in prescription drug pills send data identifying when they were swallowed.

Then, in the Proteus system, a computer chip attached to the body--either by a patch or by implantation under the skin--monitors the patient's vital stats, such as temperature and blood pressure. The aim is to correlate the pill taking with the patient's physiological responses, thereby refining the patient's drug regimen for maximum effectiveness.

Several panelists noted that such technologies raise new challenges as well as new possibilities. Neal Eigler, the manager of Savacor, a maker of implanted heart monitors, noted that doctors can be overloaded by masses of real-time information but can also practice medicine better if their patients have tools they can use to manage their own condition. Omar Ishrak of GE Healthcare pointed out that doctors and patients need to have the right data, not simply lots of data, and figuring out what the right data are is a substantial challenge.

Privacy was briefly mentioned as a potential issue during one of the question-and-answer discussions. How it's an issue wasn't explored, but one can imagine scenarios. Would an elderly parent want her children to have access to her vital statistics around the clock? Would it be a good idea for spouses to be able to monitor each other's heart rates and blood-glucose levels? Could such technology be used to monitor the consumption of recreational drugs or force compliance with taking psychoactive drugs?

Not all body computing is implanted. Michael Tchao, the manager of Nike Techlab, discussed a collaboration between Nike and Apple that had yielded the Nike + iPod system for runners. It consists, Tchao explained, of a sensor built into a Nike shoe that wirelessly sends data to a receiver plugged into an iPod. So equipped, the iPod can give the runner statistics on time, distance, and calories burned, both visually and by voice. (See "Beyond the Pedometer.")

"Running is a social sport," Tchao reminded the audience, and he demonstrated a system in which runners could upload their running statistics into iTunes to compare them with those of other runners. People could join "virtual marathons" by running at the same time that real marathons occurred, regardless of their location; this had just been done, on October 21, at the Nike Women's Marathon in San Francisco benefiting the Leukemia & Lymphoma Society.

Notably, sensory implants were not discussed. Cochlear implants--implanted devices that enable the deaf to hear by electrical stimulation of the auditory nerve--were not on the agenda. Nor were retinal implants, an equivalent technology for enabling the blind to see, nor spinal cord stimulators for pain control. Spinal cord stimulators block pain with programmable electrodes implanted in the spinal cord.

The martini-bar reception at the end was something of a relief, since it required no body computing at all. It was, however, sponsored by BlackBerry.

Michael Chorost covers implanted technologies for Technology Review. His book, Rebuilt: How Becoming Part Computer Made Me More Human, came out in 2005.