The Firefox OS Simulator was introduced in a Hacks post last month as r2d2b2g, a prototype Firefox add-on that makes it really easy to install B2G on your Windows, Mac or Linux computer. B2G is undergoing heavy development, and the Firefox OS Simulator makes it easy to stay up-to-date (the 1.0 release will automatically update… for now, it’s a simple install that doesn’t require restarting Firefox).