I recently submitted my first app for android.
It is an n-body particle simulator where the behaviour of the system is driven only by each particle's gravity.
Set up the initial conditions and watch the system evolve. Also, you can interact with the system 'shooting' particles in an angry birds style.
A fair amount of elements can be customized, like the number of particles, the particle color, the simulation speed, the collision policy, the particle mass, the gravity strength and much more.
Try it out and comment, any feedback is appreciated!