Alongside a new flagship handset (check out our hands-on with the Galaxy Nexus!), Google is announcing an all-new version of its Android OS. Codenamed Ice Cream Sandwich, Android 4.0 is a continuation and refinement of ideas that first emerged in Honeycomb, now all grown up and ready for life in a phone. Perhaps even more importantly, Android 4.0 is an open source release, which means any hardware manufacturer that wants a crack at it can download the source and sell a device with 4.0 on top -- Honeycomb never attained that status. We had a sit down with Matias, who took us through the new OS in-depth, but here are some of the highlights:

The UI has been revamped extensively, with that clean, futuristic look carrying over from Honeycomb -- although its Tron roots have been toned down just a tad, with more similarity to the recent facelift Google's web apps have gotten. Google also built its own font for the interface, dubbed "Roboto." Instead of hardware buttons, the OS now provides its own software back, home, and recent apps buttons right on the screen. The recent apps button brings up a scrolling list of screen captures of your recent exploits, but while you can swipe away clutter, that doesn't actual kill the process. Swiping also works to get rid of incoming alerts, and you can even swipe up when getting a phone call to select from a list of canned text message responses if you don't feel like picking up. Google has tweaked the keyboard to add better error correction, and there's also an in-line spell checker. The whole experience is apparently specifically designed for 720p screens, with the software buttons disappearing when you watch a movie for a full-in widescreen experience.

It's not just UI tweaks, however, 4.0's added features are numerous. For starters, you can unlock the phone with your face now (through face recognition, not a nose mash), syncing bookmarks with Chrome is now default functionality, and Google is using the Galaxy Nexus's built-in NFC for the new Android Beam app, which lets you share content, maps, contacts, apps, and more by tapping the back of your phone to another NFC Android phone. The browser has also been tweaked with an option for a desktop view of sites, and you can save a full page for offline browsing as well. Tabbed browsing works just like the app switcher. Gmail has been significantly tweaked to work within the OS's new UI paradigms. Even better, Google is adding offline email search, with 30 days of mail stored by default and longer periods available if you're feeling nostalgic. Deeper in the phone there's a visualizer that offers a useful chart of your data usage, which should help you toe that 2GB line.

There's a new Google+ app along for the ride, along with a new People app that pulls photos from Google+ to flesh out your contacts. Google is also offering a phone-friendly version of its Movie Studio app that originally debuted with Honeycomb on the tablet (a nice pair with the Galaxy Nexus's 1080p video). The camera app has added a panorama mode, "silly faces," and a background replacement mode, but there's also a whole photo editor built-in if you need to do some serious work on your photos or run some Instagram-style filters before uploading to your sharing service of choice.

Android 4.0 will be released worldwide in November, but the SDK is available now for developers to start building apps. We're still waiting on details of exactly how 4.0 will roll out to phones that aren't the Galaxy Nexus, when the source code becomes available, and where tablets fit into all this, but at least developers can start getting their apps ready for when those inevitable launches happen. Video and screenshots are after the break.

Source: Android Developers