John MacFarlane, the chief executive of Sonos, another well-known device maker, hinted in a blog post this year that Sonos was working on a way to play music through its speakers using Alexa voice control.

In an interview this spring, David Limp, Amazon’s senior vice president for devices, said that the company wanted there to be as many Alexa-linked “endpoints” around the home as possible and that Amazon did not really care who made those devices. Amazon has expanded its lineup of devices that use Alexa with its Echo Dot, a miniature version of the Echo speaker, and Amazon Tap, a portable Bluetooth speaker.

“The longer-term vision is a little bit like the ‘Star Trek’ computer,” Mr. Limp said. “Captain Kirk or Picard could sit on the bridge and ask anything and get the right answer.”

But while Amazon has made a lot of progress in this regard, it may have a hard time extending Alexa’s reach outside the home because of its weaknesses in mobile technology, analysts say.

The success of Echo has been described as a redemption of sorts for Amazon after it suffered a brutal defeat in the smartphone market with its Fire Phone, which the company stopped selling after poor sales — a misstep that has left Amazon vulnerable.

Apple and Google have clear advantages over Amazon because of their dominant positions in the mobile market. And they are pushing their versions of Alexa — Siri and Google’s assistant — as ways to control other devices throughout the home.

Apple has a technology called HomeKit that allows people to control thermostats, light switches and other devices with Siri from Apple devices. Google has announced plans for an Echo-like home speaker called Google Home.