Among the new features in Kit Kat is a new version of Google Hangouts which adds SMS integration (Google Voice users are, for now, still left hanging, but that's a post for another day). Some of us will be getting Kit Kat very soon, but others may have to wait.
Luckily, the new Hangouts isn't, as I'd previously thought, tied to Kit Kat, but instead is beginning to roll out to users already. Many users, though, will be waiting weeks for the update. If you're as impatient as I am, though, you don't have to wait. The fine folks at Droid Life have you covered. They've unearthed an .apk for the new Hangouts, which seems to work well on most devices, including my old Galaxy S2. That being said, this is an unofficial and unverified app, so be warned: installing the new Hangouts may break things. If you're undeterred, read on.
Hangouts isn't the only new app you can get your hands on: there's also a new Google Now (Google Search), clock, Gmail, even the Kit Kat launcher, which basically turns your entire homescreen into Google Search. I installed Gmail and Hangouts without a problem, but Google Now crashed when doing voice dictation, and the clocks app wouldn't install at all.