Comcast has added new Apple mobile devices to its Xfinity Mobile service.

The Apple Watch Series 4 with built-in cellular will be available for purchase beginning Friday in Xfinity stores, with customers able to pre-register for the device immediately. The Apple Watch will add $10 a month to the cost of a mobile plan.

The 9.7-inch iPad mini, the 10.5-inch iPad Air and the 10.5-inch iPad Pro are available now from Xfinity Stores nationwide. Tablet prices start at $17.62 for 24 months at zero percent APR for the mini, with no money down.

Related: Comcast Lost $743 Million on Xfinity Mobile in 2018

“We’re excited to expand our lineup of Apple devices to include the advanced Apple Watch Series 4 with built-in cellular as well as the new iPad Air and iPad mini with LTE, helping support the growing mobile lifestyle of our customers,” said Billy Stephens, senior VP of wireless devices and supply chain for Xfinity Mobile. “Combined with the range of iPhone models we currently offer, we’re bringing more value to Xfinity users with our mobile offering by providing the device that best suits their way of living.”

In a move that could significantly simplify the work of those developing applications for Apple devices, Bloomberg reports that Apple is aiming to enable them to create just one app serving both mobile and Mac computers by 2021.

Currently, separate apps must be developed for iOS, the operating system behind iPhones and iPads, and macOS, the software system that powers MacBooks and other Mac computers.

According to the report, Apple’s multi-step initiative, codenamed “Marzipan,” will spur the development of software for Apple devices, with developers needing to come up with just one app.

This certainly matters in the video market, where companies like Charter Communications, just for example, have to create multiple Apple software iterations for streaming services designed to run on Apple devices. For video, the big unanswered question is whether tvOS, the operating system that powers Apple TV, is also included in Marzipan.

Apple isn’t commenting.

Later this year, Bloomberg said, Apple plants to let developers port over their iPad apps to Mac computers using a new software development kit. Developers will still need to submit separate versions of their app to Apple’s iOS and Mac App Stores, but the new kit will mean they don’t have to write two different versions of the same underlying software code.

In 2020, meanwhile, Apple plans to release an SDK allowing the same convenience for iPhone apps. And by 2021, Mac application development would, under the plan, move to what is known as a “single binary,” merging iPhone, iPad and Mac applications into one app submitted to a single app store.

Bloomberg said that the leading edge of the plan could be unveiled in June at Apple’s annual developer’s conference.

In a move that should please Hulu’s busy, multitasking subscribers, the OTT-TV service now supports  picture in picture on the iPad, taking advantage of a new video mode that come with iOS 9.

Hulu made note of the addition when it released the iOS 9-facing version 4.6.1 of its app on Wednesday (September 16), proclaiming: “Picture in Picture for iOS9 has arrived! After starting your video, get back to that email you have been meaning to write while binging on The Mindy Project!”

Or checking Facebook or Twitter, or Facetiming with a pal.

Hulu, which has nearly 9 million subscribers, recently introduced a commercial-free plan that starts at $11.99 per month, $4 more than its ad-supported subscription offering. In July, it added enhancements to its iOS app that enable support for the Apple Watch.

Apple is taking aim at subscription music services such as Spotify and Rhapsody with Apple Music, a new music app/streaming service that will feature a 24/7 live radio station called Beats 1.

The service, to launch in more than 100 countries on June 30, will fetch $9.99 per month for an individual subscription, and $14.99 per month under a family-friendly tier that will provide access to as many as six members. Apple Music will initially be offered on iPhone, iPad, iPod touch, Mac, and PC starting June 30, and will be available on the Apple TV and Android phones sometime this fall, the company said.

Apple will prime the pump for Apple Music with a three-month free membership. Users will get to pair music purchased or ripped from CDs at the iTunes Store alongside Apple Music service’s new streaming library, which features a catalog of more than 30 million songs. The service will also include a curated “For You” playlist and tight integration with Siri.

Apple said Beats 1 will broadcast live to over 100 countries, and will be lead up by DJs Zane Lowe in Los Angeles, Ebro Darden in New York and Julie Adenuga in London.

Apple Music Connect, another element of the service, will provide an avenue for artists and fans to connect via the service, enabling artists can share lyrics, backstage photos, videos or even release songs. Fans, in turn, can comment on what artists have posted and share via Messages, Facebook, Twitter and email.

Apple also used its Worldwide Developers Conference in San Francisco to preview iOS 9, which will bring some new multitasking features, including a new Slide Over feature that lets user work in a second app without leaving the first. iPad users will also have access to a new picture-in-picture capability that enables them to resize the video window. During the event, Apple demonstrated the feature using the WatchESPN app.

Apple has released the iOS 9 beta software and SDK to developers, and will follow with a public beta program in July. iOS 9 will be available this fall as a free software update for iPhone 4s and later, iPod touch 5th generation, iPad 2 and later, iPad mini and later.

Apple also showed off the next software release for the new Apple Watch, watchOS 2, noting that it will support native applications. It’s due out this fall as a free update to the Apple Watch.

Apple CEO Tim Cook also shared a new milestone, noting that the Apple App Store has surpassed 100 billion app downloads.