I attended both Apple's and Google's developer conference keynotes last month, and I experienced strong deja vu on more than one occasion. Both companies talked about design and consistency. Both companies talked about improving back-end services. And both companies talked about new initiatives to make stuff on your phone appear seamlessly on your tablet or laptop.

"Users almost always have a smartphone with them, including when they are using a Chromebook," said Google's Sundar Pichai. "So we want to increasingly connect those experiences together, so they have a seamless experience across their devices."

At or around the time the Android L release comes out this fall, this means your phone and your Chromebook are going to be able to share even more stuff than they already do. If you have your phone with you, it can unlock your Chromebook (and if you have your smartwatch with you, it can unlock your phone). If you get a call or a text or your battery is running low, you'll be told about it on your Chromebook. Some Android apps are even going to be able to run in Chrome OS, though Google didn't talk much about the technical details.

It was all very similar to the "Continuity" feature that Apple's Craig Federighi showed off on the same stage in the same room three weeks before (at least both companies can still share a conference hall). When iOS 8 and OS X Yosemite arrive in the fall, AirDrop will be able to move files between iOS devices and Macs. "Handoff" can send e-mails, webpages, and even files from iCloud-enabled applications on iOS to their counterparts in OS X (or vice-versa). You can receive texts alongside iMessages in the Messages app, and you can make and receive phone calls from your Mac even if your phone is in another room.

This isn't about which company is copying from which—this kind of integration is a logical next step for both Apple and Google after years of moving various operating systems and services closer and closer together. This is about ecosystem lock-in. All of these features sound like great, logical ways to extend both companies' platforms, since you can often assume that someone using an Apple phone will be using an Apple computer. They're also going to make it harder than ever for you to extricate yourself from a given company's ecosystem once you've become embedded in it.

The latest front in the lock-in wars

This is just the latest volley in the lock-in wars, which have become more intense as companies like Apple, Google, and Microsoft try to get their software and services on more and more kinds of devices. The first battlegrounds were in application and media stores. If you had a bunch of songs from iTunes on your Mac, maybe you'd pick up an iPhone instead of something with Android. On the other hand, if you spent a couple of years amassing apps in Google Play, maybe you'd reach for an Android tablet instead of an iPad.

The war eventually extended to include services—think iMessage and iCloud versus Hangouts and your Google account; Google Drive versus OneDrive; Chrome password syncing versus iCloud Keychain. To its credit, Google has made many of its services available to iOS devices through its apps, and Microsoft has been building out iOS and Android support bit-by-bit for the last couple of years. Apple has done nothing to make its services available on other platforms, though, and Google refuses to make official apps for its services available to Windows phones and tablets through the Windows Store.

Now, lock-in is being baked in to new hardware and software. These new "Continuity"-type features being baked in to the next releases of iOS, OS X, Android, and Chrome are all great news for people who already use multiple devices from the same ecosystem. But if you've bought into multiple ecosystems, you'll never get a chance to use them. I can't use OS X to make a phone call or receive texts from my Nexus any more than I could use Chrome OS to tell me that I'm getting a call on my iPhone. If you actually want to use devices from multiple ecosystems (or if, like me, your job requires you to), you'll be missing the boat on all that stuff.

Ever-growing platforms

The companies that have conquered smartphones, tablets, and personal computing—Apple and Google, largely, though Microsoft is still a force to be reckoned with and Amazon is always hovering around the edges—are now looking to use their established platforms to launch new ones. The strength of iOS is only going to help drive support for HealthKit, HomeKit, CarPlay, and whatever new Apple TV boxes we might be getting in the future. Google's strategy is all about getting Android everywhere, including in your car, on your TV, and on your wrist.

Ars Reviews Editor Ron Amadeo called smartwatches "the ultimate ecosystem lock-in device" in his review of Android Wear, and it's true. We still haven't found hardware that we love, but assuming that we do, Android Wear only works with Android phones and tablets. Samsung watches only work with Samsung phones and tablets. The Apple wearable that's supposedly coming in October will almost certainly support iPhones and iPads exclusively. Most major apps are available on multiple platforms. Many of the most important services (chat, e-mail, social media) are available on multiple platforms. But there's no workaround that will let you use Google's watch with Apple's phone.

I look at the desktop-mobile integration features that are coming out this fall, and then I look at all the other platforms those companies are trying to drive. I can't help but wonder: does using an iPhone lock me into buying an Apple TV if I want a set-top box, even if I don't like things about how it looks or works? If I use a Nexus phone and Apple releases a gorgeous watch that I can't live without, will I need to switch or be doomed to something homely that runs Android Wear?

There are some glimmers of hope here. Many of the automakers who have announced support for Apple's CarPlay have also announced it for Android Auto. Google supports Chromecast-style screencasting from both Android and iOS devices for the app developers who choose to support it. But by and large, you'll still get the best experience if all your products live in the same family.

Living in-between

Of course, if I've got a Windows laptop and an Android tablet and an iPhone, all three will continue to work as they do now. I can use Dropbox or Skydrive to share files between all of them, and Gmail or Outlook.com will deliver mail to every device just as it always has. If you're already working around the inconveniences of managing two or three separate accounts to access two or three separate ecosystems, you can keep juggling them if you'd like.

But we're just entering into an era of computing where working like this is going to deprive you of some real, tangible benefits—you'll miss out on features that make it more convenient to use all those gadgets you use. If I want to stay out of Google's or Apple's media ecosystems or get one e-mail or cloud storage account that can work with every device I own, there are ways to work around that lock-in. Third-party solutions that can open OS X apps from my phone or sync notifications across all my devices may not even be possible, depending on what APIs and apps are available.

"We believe you should be able to use the right device for the moment," said Apple's Craig Federighi at the WWDC keynote. For both Apple and Google, this is true... as long as all of your devices are backed by the same company.