When customers can’t find a product on a shelf it’s an inconvenience. But by some estimates, it adds up to billions of dollars of lost revenue each year for retailers around the world.

A robot called Tally roams the aisles of a supermarket.

A new shelf-scanning robot called Tally could help ensure that customers never leave a store empty-handed. It roams the aisles and automatically records which shelves need to be restocked.

The robot, developed by a startup called Simbe Robotics, is the latest effort to automate some of the more routine work done in millions of warehouses and retail stores. It is also an example of the way robots and AI will increasingly take over parts of people’s jobs rather than replacing them.

Restocking shelves is simple but hugely important for retailers. Billions of dollars may be lost each year because products are missing, misplaced, or poorly arranged, according to a report from the analyst firm IHL Services. In a large store it can take hundreds of hours to inspect shelves manually each week.

Brad Bogolea, CEO and cofounder of Simbe Robotics, says his company’s robot can scan the shelves of a small store, like a modest CVS or Walgreens, in about an hour. A very large retailer might need several robots to patrol its premises. He says the robot will be offered on a subscription basis but did not provide the pricing. Bogolea adds that one large retailer is already testing the machine.

Tally automatically roams a store, checking whether a shelf needs restocking; whether a product has been misplaced or poorly arranged; and whether the prices shown on shelves are correct. The robot consists of a wheeled platform with four cameras that scan the shelves on either side from the floor up to a height of eight feet.

Tally takes advantage of the fact that big stores already put together data showing the layout of shelves and the arrangement of products on those shelves.

It uses a map of the store to navigate, while the shelf layout, known as a retail planogram, is used to compare the actual shelves to the ideal. The data collected by the robot is transmitted to a server, where it is analyzed and turned into alerts for the retailer.

Two of three founders of Simbe Robotics were involved with Willow Garage, a research lab and incubator created by Scott Hassan, an entrepreneur who worked with the founders of Google on a precursor to their search engine, to develop advanced robotic hardware and software. Willow Garage spawned a number of robotics startups as well as the widely used Robot Operating System software.

Tally is just the latest example of robots creeping into new areas of work (see “Are You Ready for a Robot Colleague?”). A study published recently by the consulting firm McKinsey concludes that 46 percent of most work could be automated using emerging technologies.

Simbe Robotics plans to develop other robots for the retail space in the future. “Our primary vision is automating retail,” Bogolea says. “We think there’s a huge opportunity to automate mundane tasks, to free people up to focus on customer service.”

Manuela Veloso, a professor at Carnegie Mellon University who works with mobile robots, says Tally is a clever idea for a robot. “From a technical point of view, it’s challenging,” she says, although the problem is simplified in this case because all the products are arranged on shelves.

Joe Jones, a robotics researcher and entrepreneur who was involved with iRobot and Harvest Automation, is also impressed. But he says the biggest challenge for Simbe Robotics will be getting the system to work reliably in the real world. “In a real-world environment the robot may not behave as effectively as it does in the lab or even in a supportive beta test site,” he says.