Nexus 10

We've all heard the stories that say it's impossible to develop for Android because of all the different possible screen sizes and resolutions. The flip side is that the way Android development is done, most of the time that doesn't really matter. I'm able to string together an Android application, but I'm no serious app developer, so I'm guessing the reality lies somewhere in the middle -- having a selection of screen sizes and resolutions to test on can;t be a bad thing.

If you have a Nexus 10, none of this matters. Using a tool first developed in 2011, you can use your Nexus 10 to simulate almost any Android environment. Because the N10 screen is so high resolution and has such a high pixel density you can emulate the different sizes and ppi right on the tablet with a few handy commands -- "adb shell am display-size" and "adb shell am display-density". 

Using those two commands while the screen is off will let the attached device emulate the chosen parameters when the screen is turned back on. You'll want to read all the documentation before you get started, but this looks like a great (and inexpensive) way to test your app layout across many different environments. 

Source: +Adam Powell