I've started to welcome more and more smart gadgets into my home, like thermostats, smoke detectors, locks, and lightbulbs. But I'm concerned: These devices collect data on my habits and power usage. Who has access to itor can demand access to it?

An increasing number of objectsin the home, the car, and even the officeare being embedded with sensors and are acquiring the ability to communicate. They help make up the so-called Internet of Things, a rapidly growing product category, with items that range from gratuitous (Internet-connected toothbrushes) to lifesaving (water-leak sensors that can help you catch floods in your home when they start). Google, for one, apparently expects it to be an enduring trend: In January the company paid $3.2 billion to buy Nest Labs, which makes smart thermostats and smart smoke alarms. Competing product lines include Lowe's Iris system, and a range of modular sensors made by SmartThings, a connected-home startup.

The way the companies deal with user data varies with the architecture of their products and how they link up to the Internet. For example, Nest devices collect and process data locally, but the data is sent to the servers periodically to be analyzed for feature improvements and energy reports. The company says only a handful of members of an internal-quality team see any information, and it's a mere sampling of what's generated by all the Nest products in people's homes. Of course, users themselves have access to a snapshot of their data via the company's mobile apps.

In contrast, most SmartThings products rely on cloud services to operate. For instance, a user can receive a push or text notification if a water leak is detected, or simply when a child gets home from school. The company's CEO, Alex Hawkinson, says that SmartThings analyzes some of the data to help it improve its products and services but that the information is anonymized.

"There's no way for us to know, for example, that somebody in New Jersey has an 8-year-old daughter named Katie, just because they use our system," Hawkinson says. He promises the company would try to resist any government request to access the data, though it hasn't come up. "We believe that consumers should own their physical graph, and all of the data that results from that physical graph," Hawkinson says.

Nest cofounder and engineering vice president Matt Rogers says his company has never received a government request for customer information. "Our contract with our users is that we will keep their data private," he says. The company has publicly stated that any data sharing that happens with Google, its new owner, will be transparent and require the user's permission. But Nest has also hinted that deep-data integration with Google could be coming soon. In the future, conceivably, information gathered from one's quantified home could be used for commercial purposes.

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