Siminoff has said in the past that he works "very closely" with Amazon, but was wary of the company because of its size and influence.
"To say Amazon will not compete with you is lunacy because they compete with everybody," he told CNBC. "They're like nuclear power. They are very, very powerful and you can get amazing, clean energy from them, but there's also the possibility of getting human radiation if you're not careful."
Ring's sale marks the biggest exit for an L.A.-area start-up since Unilever bought Dollar Shave Club for $1 billion in 2016. At least three local venture capital firms have invested in Ring: Upfront Ventures, QueensBridge Venture Partners and VTF.
A spokesperson for Ring said the company employed 2,000 "team members," but did not clarify how many were full-time workers. The company had 2 million customers and sales of $160 million in 2016, according to IHS Markit.
The acquisition of Ring also gives Amazon more ammunition to take on rival Google, which is expanding into video doorbells with its line of smart home hardware called Nest.
Amazon faces the risk of confusing consumers now that it has so many overlapping products, analysts said.
The tech giant already offers a smart camera called Cloud Cam, which is used for Amazon Key. And it acquired smart camera and doorbell start-up Blink in December.
"It's like here's this widget, here's that widget," said Frank Gillett, an analyst with Forrester. "Confusion would not be surprising given they've just run out and bought a bunch of companies. That's the mess they're headed into."
Amazon will have to figure out whether it wants to continue partnering with different companies or consolidate the services its hardware provides, Gillett said.
Neither Ring nor Amazon would discuss the terms of the deal. Reuters, citing an unidentified source familiar with the matter, reported that the price is more than $1 billion.