Google just announced its biggest update to the Hangouts Android app in some time, introducing a bevvy of features not seen before on the platform. In terms of utility, the biggest addition is probably confirmed phone numbers: like competing SMS-style message services, this will allow people who know you to search for your Google+/Hangouts profile with your cell phone number. It's an addition to the app that will be particularly useful to international users, who are used to this kind of contact lookup.
Other functional upgrades include a contextual tool system. This is sort of like Google Now for conversations: if the person you're chatting with should ask "where are you," you'll be given a temporary link to share your location with him or her. The location sharing function is the only contextual tool mentioned in this Googler's Plus post, but presumably this functionality could be extended in other ways. "Show me" could bring up a link to the camera app, for example. A revamped version of the timestamp will now show when the other party last viewed the conversation, and not just at what point.
The green dots are gone to be replaced by the last seen statuses
Cosmetically, Hangouts is now adding stickers. These are big, colorful alternatives to emoticons, and similar systems have likewise been seen on competing platforms. Google has posted 16 themed sticker packs, all free for the time being, for users to insert into conversations when words fail them. Video chats are also getting spruced up a bit with live filters. Simply swipe on the video feed to activate Instagram-style filters on top of the active conversation.
The update to Hangouts will be rolling out to the Play Store and Android devices with Google's typical staged system (read: slowly). At the moment the Play Store is showing Hangouts version 2.4 - we don't yet know what the new version will be, but 2.5 seems like a safe bet. [Update: it's 2.5.8. See below.] As soon as we get a copy of the relevant APK file, this post will be updated.
Source: Rhett Robinson, Google+
Update: We've got the APK. No need to wait for Google, go grab it for yourself now!
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.
File name: com.google.android.talk-2.5.81636427-22147330-minAPI15.apk
Version: 2.5.81636427 (Android 4.0.3+)