Fledgling robotics startup Marble has announced its first public-facing partnership, one that will see food delivered to hungry San Franciscans via a little ground-based autonomous drone.

Headquartered in San Francisco, Marble has been buzzing around in stealth for some time now, but an eagle-eyed tech writer spotted a Marble / Yelp Eat24 co-branded robot out on the streets last month, apparently during a promotional photo shoot.

At any rate, Marble has today officially lifted the lid on its work with Yelp’s online food-ordering service.

Yelp Eat24 is the result of Yelp’s acquisition of startup Eat24 in a $134 million deal back in 2015, and moving forward some customers will be offered the chance to have their food delivered by one of Marble’s little robots.

In addition to its tie-up with Yelp, Marble has also revealed that it raised $4 million in a seed funding round last April, led by Eclipse, with participation from Maven Ventures, Amplify Partners, and Lemnos Labs.

How it works

A handful of local restaurants have opted in to help Marble and Yelp trial the new service, with the eateries placing their meals inside the bot’s cargo bays. Customers will be texted an access code to unlock the cargo bay and receive their food.

The so-called “last-mile” delivery service will entail a small-scale roll-out initially, covering San Francisco’s Mission and Potrero Hill Districts. But it’s worth noting here that Marble’s robot will use a hybrid approach initially, meaning all deliveries are actually semi-autonomous. This means that humans will be on-hand to physically intervene, depending on the situations encountered by the robots.

Marble cofounders Jason Calaiaro, Matt Delaney, and Kevin Peterson met at Carnegie Mellon’s Robotics Institute, where they worked on the original self-driving cars for the DARPA Grand and Urban Challenges. They also worked on a number of autonomous robot projects for Google’s Lunar XPrize and NASA Regolith Excavation Challenge. The trio then reunited to form Marble in 2015.

“At Marble, our vision is to create helpful robots that improve urban neighborhood living for everyone,” said Marble CEO Delaney. “We’re creating a more efficient, reliable, and affordable way for people to receive what they need and want from their cities while reducing urban congestion and carbon footprint. Our system bolsters local commerce and unlocks the full potential of the on-demand economy allowing it to be something that everyone can benefit from.”

Marble isn’t the only company operating in this space. Starship Technologies, an Estonia-based startup created by Skype’s founders, has been testing its robots across U.S. and European cities since late 2015. Back in December, European food delivery giant Just Eat claimed a “world’s first” drone-delivered meal, using Starship Technologies’ robots in London. And a few weeks back, Domino’s announced a similar trial for pizza deliveries in a handful of European cities.

Robots aren’t just encroaching into the food-delivery realm, however. Soon it could be quite feasible for your meals to be ordered, made, and delivered without a human in sight. Domino’s is already offering a pizza-ordering service through a Facebook Messenger bot, while Mountain View-based Zume Pizza is operating a commercial kitchen using robots to apply and spread the sauce on the base, while another places the pizza in the oven.

Marble’s robot uses similar technology to that of Starship Technologies and, for that matter, self-driving cars. They are capable of navigating busy thoroughfares using in-built sensors and cameras, while simultaneously mapping the sidewalk to optimize its route. A spokesperson said that Marble plans to map the “majority” of San Francisco’s sidewalks over the next year, as it ramps up its plans for robot-based food deliveries.

It is worth stressing here that it is still very early days, and there are still many hurdles before food deliveries from robots are carried out entirely autonomously. Though the cargo bays are locked, meaning nobody aside from the customer can access the food, there are still external forces that could interfere with a robot’s journey from A to B. What is stopping a prankster from throwing a large piece of tarpaulin over the robot to obstruct its view? Or maybe even smear some mud over the camera and sensors? This is why Marble’s robots will be chaperoned by a person initially, and it’s difficult to envisage a time in the near future when these machines are left to function completely off their own volition.

“With the rapid growth of the on-demand and e-commerce markets, solving the last mile delivery problem is incredibly important,” said Greg Reichow, general partner at Eclipse. “The existing solution of using 3000lb fossil fuel burning, city-congesting cars does not scale. We invested in Marble because of their groundbreaking technology and exceptional team.”