Edge Reflow is coming soon, enabling designs that change in response to varying screen sizes (phone, tablet, desktop, etc.):
Create responsive layouts and visuals with standards-based CSS. Edge Reflow offers an HTML-based design surface, enabling web designers to accurately and confidently realize their visions throughout design and development.
Check out a sneak peek:
Can’t wait to see the integration with Photoshop!
ps. Also i would like to see these features in Muse.
I second the desire to see this technology in Muse.
There is undoubtedly a market for such a tool. Work visually, but output CSS instead of pixels. Hopefully it works. I also hope this project doesn’t involve whoever gave the go-ahead to the name “Phone Gap Build”.