Dual App Multitasking
With the 720p displays coming out, we have a lot more room on our phones than ever before. One of the things I love about having more space on a widescreen display is having two windows open side by side. In Windows 7, the auto resizing of the windows by dragging them to the corners is such a handy trick when you need to reference one document while composing another.
I would love to use this functionality on my phone as well. As a former webOS user, I always dreamed of the day where I could have 2 cards open side by side. The closest I ever got was this mockup in the Precentral forums (from bhughes719).
Having one document open for reference while working on another is a key functionality for content creation. I can't count the number of times I've had to double tap the home button on iOS to switch over to the material I was referencing. We shouldn't be limited to one full screen app when our screens are approaching 5".
Example applications: Replying to an email, summarizing a document, taking notes, comparing two images, comparing two spec sheets, practicing a presentation (write up your notes while viewing a slide on the way to a meeting). Running two apps simultaneously would boost my mobile productivity exponentially.
I'm really searching for the mobile solution to having two windows open. Hopefully Windows Phone or Android will incorporate something like this. I think iOS could have a mobile interpretation of Spaces that would work pretty well too.