Firefox OS Simulator Now Available
Browser-based simulator for Mozilla’s upcoming OS for mobile phones
Exceeding 65 MB in size, the add-on is a huge download and works on Firefox 16 and above. After installation (no browser restart is required), you can find it in the Web Developer section of the browser. Updates are installed automatically.
Because it actually runs B2G Desktop, Firefox OS Simulator runs smoothly and startup times are very fast.
... so hot right now