After some teasing, Paranoid Android has unveiled (in a lovely promo image) their plan for multi-window functionality on Android, which they promise to "get right," – Halo.
The premise is simple, yet extremely ambitious in scope – allow apps to give you notifications right on top of your screen, which allow you to pop into that app without leaving the one you're in (no matter what it is), take care of business, and resume your experience uninterrupted. The general concept, which rejects the notion of a distracting notification shade, and shuns implementations like "whacky s-multiwindow," is no doubt inspired by Facebook's admittedly awesome Chat Heads functionality, perhaps the most compelling feature of its new Home app.
From a user experience perspective, Halo looks great, and promises to provide a welcomed change from the pull-down shade in favor of a more visually rich and thoughtful method of jumping between apps.
Some of you may remember Cornerstone, a multi-window-ish implementation CyanogenMod toyed with for a brief time before Googler Dianne Hackborn explained the issues with Cornerstone as she saw them, what it might do to Android compatibility, and what the consequences may be.
If you're worried Halo will face the same scrutiny, PA says simply don't be. Paranoid Android emphasizes that Halo's implementation is written "from scratch," and will (theoretically) pass Android's compatibility test suite. A Google+ post explains the technical underpinnings of the system for those interested in a more detailed explanation.
If you're a Paranoid Android fan (or just someone who's yearned for a decent multi-window implementation), keep an ear to the ground – Paranoid Android has not made an official announcement regarding the expected completion of the project, or when you'll be able to get your hands on Halo, but progress so far seems promising, to say the least.