I have a Surface Pro 3, Microsoft's high-end tablet that can also serve as a laptop replacement (provided you purchase the $129 type cover). The Surface Pro 3 runs Windows 8.1 Professional (and soon will be running Windows 10). I also have a Google Nexus 7 Android tablet that runs the Android 5 (Lollipop) operating system. There are many Android tablet productivity apps for my law practice I find useful on my Nexus 7 that I wish I could run on my Surface Pro 3. Now I can.
The app store for Microsoft's tablets and computers is tiny by comparison to either the Android app store (Google Play) or Apple's iOS app store. The Windows store does not offer the same apps or equivalents available on an Android tablet or an iPad. Fortunately, American Megatrends (AMI) offers a version of the Android operating system you can easily install and run in a "virtual machine" on a Windows tablet. This works particularly well on the Surface Pro 3 because it has the processor and RAM horsepower to effectively run a virtualized second operating system. Lesser tablets, like my Dell Venue 8 Pro, can run the virtual version of Android, but it gets a bit laggy, particularly in full-screen mode.
The Android virtualization software is called AMIDuOS. It sells for $9.99, but also has a 30-day free trial. I am currently on my free trial and have been impressed with how well it runs on the Surface Pro 3 (mine is the Core i5 version with a 128 GB SSD and 4 GB of RAM). The excellent Surface Pen works fine with the Android apps I've installed, particularly my favorite PDF reader and annotator, iAnnotate.
Once installed and updated with a free download from AMI's web site, you have full access to the Google Play store and can link it with your existing account. That means you can download all of the free and paid apps you have on your other Android devices without incurring additional charges.
I had some initial trouble getting AMIDuOS to start, but the web-based tech support offered by AMI quickly produced a solution. The antivirus program I used, Avast!, was blocking AMIDuOS from creating its required virtual machine. I'd been meaning to switch to another excellent and free antivirus program, Avira. Once I switched, AMIDuOS worked fine.
Although I still have a lot to learn about using Android via AMIDuOS on my Surface Pro 3, I can tell even at this early stage that it will make my device a much better mobile productivity companion.
If you don't need or want to run a full "virtualized" Android operating system within Windows, but just have an Android app or two you'd like to run on your PC or Mac, that is also now possible - so long as you use Google's Chrome web browser.
In this article from The Verge, read about Google's new ARC Welder app for Chrome that will let you convert Android .apk app filed to apps that can run within the Chrome browser (or in the Chrome operating system on a Chromebook). So it now appears that Android apps are as close to universal as they can possibly be. You can run most of them on any operating system except iOS. Perhaps that is coming someday too.