When Amazon’s chief executive, Jeff Bezos, promised in 2013 that drones would soon be flying everywhere delivering packages, a miniature camera whirring through homes and recording video was probably not what people envisioned.

But on Thursday, Amazon’s Ring division unveiled the $249 Ring Always Home Cam, a small drone that hums as it flies around houses filming everything, ostensibly for security purposes.

Amazon also introduced new Echo devices, a cloud gaming service called Luna and other products. But the home security drone stood out. The company’s promotional video highlighting the camera showed a burglar breaking into a home and getting spooked as the drone flew straight at him — “Oh, no!” he exclaimed — while the homeowner watched the encounter on his phone.

“Oh, yes,” the ad proclaimed.

Reaction to the surveillance drone was spirited — but not in the way Amazon might have hoped.

“In a country with no laws regulating digital privacy, anyone who buys this from a company with a history of privacy problems is insane,” tweeted Walt Mossberg, a longtime tech product reviewer who is a member of the nonprofit News Literacy Project’s board.

Ring said the drone could be used to check whether a homeowner had left the stove on or a window open, and promised that it would record only while flying. It would also make a humming sound so it would be clear when it was filming. But privacy was still the primary concern for most flabbergasted Twitter users.

“An internet connected drone camera for your home, owned by Amazon. this definitely won’t be a privacy nightmare *at all*” one person tweeted.

“A scary step in the future of tech?” posted another Twitter user, Khoa Phan. “Like it’s cool but always eerie at the same time. Obviously there’s some concerns about privacy with Amazon. But what’s the next step after this if this is just the beginning!?”

A disclaimer at the bottom of Ring’s blog post announcing the drone said the device had not been authorized by the Federal Communications Commission — and might not ever be authorized. Ring said the drone would become available next year, but not “until authorization is obtained.”

As for Mr. Bezos’ plan to have drones delivering packages? Back in 2013, he said it might happen within around five years. To date, it has not.