This is an app that lets you control a Arduino that will change a light in a room on and off. Here is the "How To" on this project https://gist.github.com/Aflynch/71da4fce926e1e452ddf . Let me know if you have any questions? Or if you would like me to build out Android apps to drive homemade robots?
Really if you have a cool idea that you would to see built just let me know :)
Also if you care there is a hidden button to change the look of the app.