“Stretchable electronics” will be able to measure heart rate, brain activity, body temperature and hydration levels.

Very soon, we will see inside ourselves like never before, with wearable, even internal , sensors that monitor even our most intimate biological processes. It is likely to happen even before we figure out the etiquette and laws around sharing this knowledge.

Already products like the Nike+ FuelBand and the Fitbit wireless monitor track our daily activity, taking note of our steps and calories burned. The idea is to help meet an exercise regimen, perhaps lose some weight. The real-world results are uneven. For sure, though, people are building up big individual databases about themselves over increasingly long periods of time. So are the companies that sell these products, which store that data.

That is barely the start. Later this year, a Boston-based company called MC10 will offer the first of several “stretchable electronics” products that can be put on things like shirts and shoes, worn as temporary tattoos or installed in the body. These will be capable of measuring not just heart rate, the company says, but brain activity, body temperature and hydration levels. Another company, called Proteus, will begin a pilot program in Britain for a “Digital Health Feedback System” that combines both wearable technologies and microchips the size of a sand grain that ride a pill right through you. Powered by your stomach fluids, it emits a signal picked up by an external sensor, capturing vital data. Another firm, Sano Intelligence, is looking at micro needle sensors on skin patches as a way of deriving continuous information about the bloodstream.

Make no mistake about these companies’ ambitions. “Ultimately, we see ourselves as a part of the healthcare ecosystem,” Amar Kendale, MC10’s VP of market strategy and development, said in an e-mail. In this future, he wrote, “data will need to be shared seamlessly between customers, providers, and payers in order to reduce heathcare costs and simultaneously deliver the best possible care.” Proteus hopes to use anonymized data from its customers to understand health patterns over an entire population, presumably to revolutionize medicine.

Those are not just lofty goals; they make a lot of sense. If this kind of information exists for a lot of people, it is arguably folly to not look for larger trends and patterns. And not just in things like your electrolyte count, because overlays of age, educational level, geography and other demographic factors could yield valuable insights. The essence of the Big Data age is the diversity of data sets combined in novel ways.

What is missing is much of a sense of what this is worth, and what it may cost, and the terms under which we’ll turn our data into a product. Nike and Fitbit already log a lot of personal data, and it is not clear what, if anything, they plan to do with it.

Nike acknowledged an e-mail asking for details about its plans, but did not get back after that. The software license for Nike+ does say that “Nike+ Product Software may include software that collects information about how you use your Nike+ Product,” but has no further details about what this means. Fitbit did not respond to e-mails.

Proteus says its customers will own their data and may share it, but must also grant the company permission to use it for product development and the cultivation of its data sets. As Mr. Kendale stated, MC10 sees data sharing between people and companies as something of a necessity.

For those of you troubled by Facebook claiming the right to know whether you like cats when you sign up, this is probably a significantly bigger deal. Others may not care, or even see themselves as actors in a global project to understand ourselves as never before. What may be troubling to all, however, is the haphazard way these new behaviors will be captured and determined. There are likely to be different strategies depending on company, country of use and whether the product is looking as something regulated, like a drug, or open, like a heart rate.

Those legal and corporate distinctions, of course, were all developed in a world where we weren’t able to see so much of each other, or deduce one behavior by crunching the data from several other sources.

There are also movements to use this data in entirely new ways, for patient-generated medical research. Linda Avey, who co-founded the personal genetics company 23andMe is now working on a start-up called Curious, which should be live by the middle of next year. Her idea is to get people with difficult to pin down conditions like chronic fatigue, lupus or fibromyalgia to share information about themselves. This could include the biological data from devices, but also things like how well they slept, what they ate and when they got pain. Collectively, this could lead to evidence about how behavior and biology conjure these states.

“All of the devices that are coming on the market will shuffle their data into different environments,” she said. “They are starting to realize that they can’t just be the keeper for that.” She hopes the companies will allow for common sharing of the individual data, leading to a kind of open source branch of medicine. So far, she said, few if any have committed to that.