My plan is to build one same mobile application for iphone, android, windows phone 7, blackberry, (nokia) and (bada) and blog my experience with each of the platforms.<p>Any suggestions on what I should build?<p>One of my ideas was to build a mockup viewer for balsamiq.<p>I will be spending around next 1.5 months on this. Only constraint is it should not be a 3d game. Anything else is fine :)<p>For each of the platforms I will be using the tools and sdks for that platform ie no cross platform frameworks. I will periodically blog experiences with each platform and release the code under MIT license.<p>So let the brainstorming begun :)<p>p.s. If any startup wants to utilize my marathon to get their mobile app built, I would be more than happy to do it for free as long they are fine with taking over the project once I have released the v1