In the past, I'd taken a couple of stabs at teaching myself how to code in Android. The setup, however, turned me away on the first couple of tries. Installing the Java developer kit and then the Android Development Tools and all of the SDKs seemed like a lot of work. And if it was that much work to install, it was going to be even more to learn. Eventually, I did it, and I enjoy programming for my phone.
Recently, I found an app for my Tablet and phone that let's you develop right on the device itself. AIDE is a free/paid Android IDE. It requires little to no setup to start coding. Simply switch to expert mode and you can code using either Eclipse or Gradle as your platform. Best of all, when you're ready to try it out, you simply run it from AIDE and it loads straight to your phone. No more emulators or connecting your phone to your computer.
You can store files locally or on DropBox or using Git. However, Git pushes do require the upgrade. You can also clone GitHub projects in the App and run them. This is something I find to be unbelievably useful.
With the free version, you're limited to only being able to save apps with a limited number of classes and files. This was the reason I actually went with the upgrade.
If you buy a subscription, you can actually watch tutorial lessons. I can't comment on the quality of the lessons as I have not watched them and probably won't.
So who is this for? I'd recommend it for those interested in giving Android Development a try but are intimidated by the desktop setup. You won't get as much help from AIDE in terms of auto-completion as you would Eclipse or Android Studio, but the fewer hassles are worth it. Additionally, if you're interested in easily cloning and installing GitHub projects, it seems like a no-brainer to me.