Coming, Ready or Not: Cell Phones as Sensors

A look at how one city is using cell phones as sensors to keep tabs on everything from traffic to crime, and why some government leaders say this is the wave of the future.

In the Mexican city of Tuxtla Gutiérrez in Chiapas state, an interesting experiment is unfolding that could be an early forerunner of a future trend—the use of cell phones as sensors.

Under the city's "Vigilante Taxi Driver" program, cab drivers use GPS-enabled cell phones to send messages and photographs about everything from accidents and potholes to burst water mains, downed streetlights and criminal activity—effectively acting as additional eyes and ears of government to combat high crime rates and run-down infrastructure. The reports go to a control center for routing to the appropriate government agency.

The US$1.15 million program has been a resounding success, generating close to 10,000 reports a month from 3,500 drivers and helping recover stolen vehicles, identify counterfeiters, dismantle kidnapping and car-theft gangs and, in some cases, save lives. Little wonder the Chiapas government recently expanded the program to two more cities.

"It's proving to be a great tool for the government and for drivers," says José de Jesús Penagos Nangulari, head of the Logistics Department at the Secretary of Transportation in Tuxtla Gutiérrez. "The government cannot be everywhere at once."

The program won recognition last year by the Intelligent Community Forum, a New York-based smart-city think tank, prompting co-founder Robert Bell to call it "a near-perfect blend of technology and citizen participation."

Citizen-Owned Sensor Networks

The concept of using a simple, ubiquitous technology like cell phones to engage citizens in improving their community is resonating far beyond Chiapas. At least one U.S. city government official has predicted that citizen-owned smartphones will increasingly form the municipal sensor networks of the future. And companies like Intuit are working to reimagine their products to be "mobile first" or "mobile only"—for instance, by considering how they would take advantage of sensors in smartphones.

Meanwhile, researchers are experimenting with putting sensors into cell phones to solve social problems—controlling the spread of diseases, for example, or collecting environmental data on air pollution or radiation—with little or no citizen input required.

Over the next decade, as the Internet of Things ramps up—and its next phase, the Internet of Everything—wireless sensor networks will become an increasingly pervasive form of instrumentation for the gathering and analysis of data of all stripes. But deploying large-scale sensor networks can be cost prohibitive, especially in developing countries. But cell phone networks provide a powerful, ready-made and pervasive wireless infrastructure with massive economies of scale to boot.

"By their sheer numbers, cell phones provide an opportunity to gather geospatial data with much higher granularity and more penetration than previously possible," says RJ Honicky, a former researcher at the University of California, Berkeley and Nokia whose work was a call to action to the industry to consider cell phones as sensing systems.

Problem Solving in the Developing World

Some problems are better suited to mobile sensing than others. For example, cell-phone sensors have great potential for monitoring pollution, which usually concentrates in densely populated areas—where cell phones abound.

"The action is where the people are," says Honicky, now a senior software engineer at Tarana Wireless.

Honicky has already tested a prototype cell phone containing a carbon-monoxide sensor capable of sniffing out the lethal gas and thus saving lives. To help measure air pollution, other researchers at Berkeley have succeeded in miniaturizing aMEMS particulate matter sensor—normally the size of a shoebox—so that it fits inside a cell phone.

Elsewhere, researchers have focused on using cell phones with sensors to create an early-warning system for modeling and predicting the spread of tuberculosis in South Africa, and using cell phones in tandem with water quality sensors to monitor village water supplies.

There's a Sensor for That

The potential applications extend beyond the developing world. Honicky says sensors in cell phones could control temperature in homes and offices; detect emergencies, such as an elderly person's fall or a lack of motion; and "slurp up" data stored in delay-tolerant networks as a person walks past a nearby node, with the cell phone functioning as a data mule.

And as smartphones become even smarter, experts say they will come loaded with even more sensors, such as altimeter sensors that can tell you what floor you're on in a building, and sensors that can detect perspiration to monitor your excitement level and mood, which could become incorporated in video games that will factor in emotion during gameplay.

For now, the cell phone-as-sensor approach is still largely in the idea stage, due in part to issues of size, cost and energy use. Honicky says sensors need to be small enough that they can fit inside increasingly sleek phones without adding bulk, cheap enough that they don't send phone costs soaring, and energy efficient enough that they don't drain a phone's power. All of these challenges will be solved in time, Honicky says.

More problematic, he says, are the massive privacy issues that will come with embedding sensors in smartphones that, arguably, already know and transmit too much personal information.

"You have to earn people's trust," Honicky says. "In the long run, that will require giving control of privacy to the user, and being transparent about how the data is being used."

There may soon be a sensor to help with that, too. Some companies are embarking on a race to develop privacy-protecting sensors and databases.

"It's like an arms race," Honicky says.

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