The funny thing is that you may not even need a job once you do something great on your own :)
If you are short of money, you can always get a simple part time job to survive.
1) It let me set the tone and path for much of the interview, since so many places do unstructured interviews. 2) It was a concrete demonstration of my skills. 3) Java and mobile are both hot technologies, and the game also made effective use of other common stuff like Open GL, multithreading, network, database storage (via sqlite), etc. 4) Spending a few minutes playing a game sets a relaxed tone for the entire interview, which makes things easier for everyone involved.
Structured interviews really are a brilliant strategy. Whenever I interview, I do my best to subtly direct the interview in a way that exposes my strengths and leads the conversation into areas that I am most comfortable with (and trust me, whipping out a concrete example full of technologies that you're absolutely comfortable with helps). A structured interview, to an extent, would allow the employer to retain better control of the interview (whether or not the realize it), which is probably to their benefit. For instance, I teach Java, C#/VB, and some other modern languages at a local college after work, do tons of C / embedded / network / etc. stuff at work, and do digital electronics for hobby ... so if you let me push the interview in those technical directions, I'm at an advantage.
I am always surprised when I meet mobile developers who have never created a mobile app for themselves.
This is a good idea.
I have no idea what people would want or what I could make that people would want or what open problems are there that I could make. Every idea I have someone else already has a better solution.
I keep trying and put it in github but it's mostly for me; no one looks at it.
The Julia people are complaining that their language is great but it is not being picked up because their standard libraries are missing a ton of functionality.
Start knocking out some standard library functionality.
Sure, you may not be interested in Julia. But there are plenty of other projects out there that are understaffed. IPython Notebook needs developers. Octave needs somebody to write a good front end. It goes on and on.
The advantage is that you don't have to be super creative (compare Julia's libraries to Python, and start implementing something that isn't yet in Julia), nor predict the future (meaning, you can make a brand new X, but if the world goes to Y, you will never get picked up). What you write will be used by (at least) thousands, and you will have to write production quality code to get your pull requests accepted. I'd be impressed with anyone that did that, even if I had no interest/need in the project that they contributed to.
Whatever you made will probably be something pretty sweet because you chose something close to your heart, not something that was simply 'unsolved' or 'needed doing'.
Employers will love that you chose to challenge yourself to build new skills as a hobby, and because you chose something that you are passionate about, you'll probably also have a good amount of enthusiasm while you talk about it, which is equally important.