In 2013, entrepreneur Jamie Siminoff left the set of Shark Tank without a deal for his video doorbell company--and in tears because his company was almost out of money. Five years later, Amazon is buying it for a cool $1 billion.

Next time your doorbell rings, wouldn't it be nice if you could look at your smartphone and see who's there? Siminoff thought so, so he rigged up a Wi-Fi-enabled camera outside his door. In his case, it was something of a necessity, since he spent his days in his garage trying to dream up new product ideas, and couldn't hear the doorbell from there. But when his wife said it made her feel safer, he realized he'd hit on a great new startup idea.

He dubbed his company DoorBot and went to work, eventually hiring seven employees. But getting a hardware company off the ground is tough, and a year later, when he landed a coveted spot on Shark Tank, DoorBot was close to running out of money. 

The team went all in for Shark Tank, building a $10,000 set that the company could ill afford and working hard at prepping and rehearsing for an entire month before going on the show. But the Sharks didn't bite, and Siminoff left, dejected. He knew that not only would DoorBot not receive badly needed funds from the Shark Tank investors, but also because he didn't get a deal, it made it less likely that ABC would air the segment, depriving DoorBot of the free publicity it could bring. But then the segment did air, and it brought a huge increase in sales that continues to this day, plus lots of interest from investors including Richard Branson. Despite the Sharks' rejection, DoorBot began to thrive. In November, in a Shark Tank update, Siminoff reported that the company, now called Ring, had 1,300 employees and 10 products sold in 1,600 stores.

He also said the company was now valued at $1 billion, and Reuters tweeted a few hours ago that Amazon had acquired it for at least that much. 

Amazon seems to be racing to compete with Google and Nest for the smart home market, and acquired another smart doorbell company, Blink, in December. It also invested in Ring last year through its Alexa fund, and Ring created an Alexa skill, allowing users to interact with the Ring doorbell through their Amazon Echo devices. 

As for Siminoff, he doesn't seem to have made any public statements since the news broke. He's probably off celebrating somewhere.