See a great iOS or Mac App Store app and want to share it? Not a problem. Copy the link, and you can send it through mail, messages, social networks, or post it on the web. If the link is for a Mac app and you're on your iPhone, though, it starts to become a problem. If the link is for an Apple TV app, well... it can't be, because there's currently no way to share Apple TV app links. But what if there was? What if you could get any App Store app on any Apple device—or even from the Web?
The platform jail
Right now, if you're on a Mac and you click on an iPhone or iPad app, it'll open on iTunes and let you download it. Then, when you're back on your iOS device, it will either have downloaded automatically, or you can get it from your purchased list. It works fine.
If you're on an iPhone or iPad and attempt to do the reverse, however, you get a page telling you that app is only available on OS X with a link to learn more... which will sometimes take you to the iOS version of the app instead. It's confusing.
But it's still better than the poor Apple TV, where the only way to get an app is to go to your device's App Store, search for the program, and pray you can find it. (Luckily, there are few enough apps right now that the App Store's lack of search prowess doesn't get in the way, but this won't be the case forever.)
The great web escape
Instead, imagine if the web intermediated, providing all App Store links on all platforms. Click on an App Store link on your Mac or PC and, instead of iTunes, you go to iTunes Preview and there's a Get or Buy button right there. Click the button and you can choose to open in iTunes or log into your Apple ID account and initiate the Get/Buy right from the Web.
Instead of iTunes Preview, though, it's now App Store for iCloud, or whatever best fits the model Apple wants to use.
Same with iPhone or iPad: Since those are single-user devices, iOS apps can automatically redirect to the App Store app. Mac apps, though, could launch the iTunes Preview page in Safari and offer the same opportunity to log in and initiate a Get/Buy from the Web.
This would also work for getting Apple TV apps from iPhone, iPad, or Mac. Tap or click on the link, go to the Apple TV app page on App Store for iCloud, and tap or click to begin the Get/Buy process.
Here's a (really bad) mockup.
Since App Store for iCloud—like iTunes Preview—pages could show up in Google and other search results, it would also make it easy to find the links for Apple TV apps, making sharing possible to begin with. At least on every device but the Apple TV....
To share from Apple TV would still be a challenge, since it doesn't have any mail, message, social, or Web/WebKit integration. Perhaps handing off to an iOS device could work?
Since you can already buy iOS apps on the Mac, the process for buying apps for one device on another is likely simple and secure enough that additional safeguards aren't needed. There's an argument to be made that customers might get confused over which app is for which platform, but clear branding and presentation can handle that.
If Apple believes security and the potential for confusion warrants additional safeguards, though, any download could require confirmation on the destination device.
In other words, if you Get/Buy a Mac or Apple TV app on your iPhone, the next time you use your Mac or Apple TV, and App Store prompt could pop up asking for password or Touch ID authorization to complete the purchase/download. You could also opt for auto-download if the added security is too onerous for you.
iOS 10 and beyond
I have no idea how complex this system would be for Apple to implement, given the existing iTunes architecture. But it's something its competitors already provide. You can browse Google Play apps right from the web and send them to any Android device connected to your account. Same for Amazon Kindle content—and that content can even go to iOS devices. It's something that's conspicuously absent from not just the capabilities but the convenience of Apple's ecosystem.
The ability to get apps from any device—at any time, anywhere—wouldn't just make the experience better: It would make the platforms more valuable for customers, especially the iPhone and iPhone owners, since that's the device most of us have with us most of the time.
Hopefully the App Store team is on it and we'll all be able to enjoy universal App Store purchasing sooner rather than later.