Walmart employees can now deliver groceries directly to customers' refrigerators when they aren't home.

The new Walmart InHome Delivery service, which was announced at Walmart's shareholder's meeting in June, was officially rolled out on Tuesday. CNBC was first to report the news.

It is currently limited to customers in Kansas City, Pittsburgh, and Vero Beach.

Walmart workers gain access to customers' homes using smart-lock technology controlled from a mobile phone. These employees are fitted out with a camera that records the delivery process and customers are able to live stream this video.

Amazon is already offering in-home delivery services. In the past three years, it has rolled out in-home delivery, in-car delivery, and most recently in-garage delivery.

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Competition in the US grocery sector is heating up.

Walmart has officially launched its new in-home delivery service for customers in Kansas City, Pittsburgh, and Vero Beach.

These customers will be now able to have groceries delivered directly to their fridge by a local Walmart worker when they're not at home. It costs $19.95 a month for unlimited deliveries on any orders at $30 or over (excluding tax).

The new service was announced at Walmart's shareholder's meeting in June.CNBC was first to report the news of its official launch early Tuesday morning.

Amazon is already offering similar in-home delivery services. In the past three years, it has rolled out in-home delivery, in-car delivery, and most recently in-garage delivery.

It is another example of how the two retailers are battling it out to create the most convenient online grocery shopping experience.

How does it work?

Customers who opt-in for Walmart's new delivery service have a smart lock fitted to their front door or garage door. This costs $49.95 but the installation is free. The customer then orders their groceries online and are notified when an associate is headed to drop it off.

Walmart workers access customers' homes using the smart-lock technology, which is controlled from a mobile phone. They're fitted out with a camera, which records the entire delivery process and can be live-streamed by the customers.

To ease concerns over the safety of this new service, Walmart says that the front door will not open if the camera isn't recording and once the associate locks the door, they are unable to re-enter. The customer then receives a notification to say that the delivery is complete.

Walmart writes online that deliveries are done by its "most reliable and trusted associates." These workers must have worked at a local Walmart store for at least a year and undergone multiple background checks.

This isn't the first time that the Walmart has tested out in-home delivery. In 2017, it announced a new partnership with smart-lock startup August Home to test in-home delivery in Silicon Valley. But since then, Amazon has powered ahead with its own options.

This new service not only helps to make delivery an option for customers who might not otherwise have considered it but it could help Walmart to prevent the number of items that are stolen from people's doorsteps.