The device will monitor people's basic health metrics using ambient sensors, with a focus on whether someone is making frequent trips to the bathroom or spending more time than usual in bed. Comcast is also building tools for detecting falls, which are common and potentially fatal for seniors, the people said.

These people asked not to be named because they were not authorized to speak on behalf of Comcast, and Comcast declined to comment. (Comcast owns NBCUniversal, the parent company of CNBC.)

A team under Sumit Nagpal, a senior vice president and general manager of health innovation at Comcast who previously worked at the consulting firm Accenture, has been working on the device for more than a year, according to two people with direct knowledge. Nagpal joined Comcast in February of this year, according to LinkedIn, to build a strategy and a team for bringing the new health hardware to market.

Comcast plans to offer the device and related service to at-risk people, including seniors and people with disabilities, but the timing, pricing and roll-out plan have not been finalized. It will start to experiment with pilots, which are not limited to Comcast customers, by the end of 2019, with potential commercial release in 2020.

Unlike most home speakers, the device won't be positioned as a communications or assistant tool, and won't be able to do things like search the web or turn lights on and off. But it will have a personality like Alexa and it will be able to make emergency phone calls in the case of a health event, the people said.

The device would be a first for Comcast in health, but it already offers hardware and services focused on home security and automation. Comcast has experience in voice with a remote that responds to commands, which people mostly use to search for TV shows and movies. The company began exploring opportunities in the health sector a few years ago, and last year set up a partnership with insurer Independence Health Group, which is initially focused on the group's employees.

The move would bring Comcast into competition with a number of technology companies, including Google, Amazon and Apple, which have also explored how to help older people "age in place," or live independently for as long as possible. Google is looking at using its Nest and Google Home devices in senior living facilities, Apple added fall detection and heart health tracking to its smartwatch, and Amazon has been exploring opportunities in tech for the growing aging population for several years.

Comcast might also have an edge with this population because of its access to the home through its cable and broadband business, which involves technicians showing up to people's homes for installation and upgrades. In theory, technicians could set up the device during those visits.

In addition to developing new hardware, Comcast has been in talks with several large hospitals, including Rush in Chicago, said a person familiar with the conversation. The discussions with Comcast have centered around using the device to ensure that patients don't end up back in the hospital after they've been discharged. Increasingly, hospitals are getting penalized by the federal government for failing to ensure that patients don't end up right back in the emergency room, and are looking into tools to monitor patients remotely.

Disclosure: Comcast owns NBCUniversal, the parent company of CNBC.

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