"Alexa" is coming to mobile — provided that mobile device is made by Amazon.

Amazon today announced a new tablet, the Fire HD 8, which bears the same name as the Fire HD 8 tablet before it. The new tablet has the same 8-inch, 1280 x 800 resolution touchscreen display like its predecessor; but is also built with 50 percent more RAM (1.5 gigabytes), double the base storage (16GB or 32GB), and a larger battery that Amazon claims will last up to 12 hours.

It is, for all intents and purposes, a very decent piece of tablet hardware, all for $90. And Amazon says its approach to making lower-cast tablets is working: Kevin Keith, the company's general manager of Fire tablets, said that sales have more than doubled in the past year, with last year's $50 7-inch tablet emerging as the best-seller of all of its tablets (at least, by its own internal metrics; Amazon famously doesn't share information around unit sales).

But the Fire HD 8's most notable feature might just be Alexa, Amazon's voice-controlled assistant. The previous Fire HD 8, the best-selling seven-inch tablet, and Amazon's Fire HD 10 tablet will also get Alexa, through an eventual software update to Fire OS 5.

Amazon wouldn't say exactly when the software update will be rolled out, except that it's in "the coming months." But when it does become available Alexa on an Amazon tablet will be able to do mostly everything that Alexa does on Amazon's other devices — read the news, tell jokes, set timers, call an Uber, and more. Amazon's Keith says the company thinks Alexa will be used mostly for pulling up entertainment, given that the tablet is designed primarily to be a consumption device.

Amazon will also take advantage of a tablet display to show "cards" of information based on voice queries, which sounds similar to the information cards Google shows if you've opted into Google Now on your Android device. So if you ask Alexa for the weather from the tablet you'll get a visual display of the weather, as well as a forecast for the upcoming week; same with music requests, sports scores, timers and alarms.

The announcement of Alexa on Amazon's own tablets is significant mostly because it's the first instance of the popular virtual assistant on mobile. Until now Alexa has only been available on the Echo speaker, the smaller Echo Dot, the Amazon Tap speaker, and Amazon's newer Fire TV gadgets, while the Alexa mobile app has served as a manager app for the AI on those pieces of hardware.

It won't be the same Alexa experience you might get on the Echo speaker, because of the lack of far-field speakers and the need to push the home button to get Alexa going on a tablet. Arguably, shouting at Alexa from across the room is a much better use case than pressing a button, as with the Amazon Tap portable speaker. (Even Siri responds to a vocal "Hey Siri" on iOS.) But it's still a move by Amazon to put its AI onto mobile, at a time when almost all of the major consumer tech companies are pushing artificial intelligence on mobile devices in some way.

Not surprisingly, Amazon won't say whether Alexa will ever come to other mobile devices, like Apple's iOS devices or gadgets running on Google Android. Just as Siri is limited to Apple's mobile, wearable, and smart home platforms, Alexa may very well be limited to Amazon's own ecosystem.