Google Hangouts is already an extremely good instant messaging service. One of our favorite Hangout features is the fact that you can start a conversation on one device and seamlessly continue it on another without any glitches.
Google has announced that a new version of Hangouts for Android and iOS will go live sometime today. The major change implemented is SMS integration. Much like iMessages on Apple's iOS, Google Hangouts will choose the appropriate mode to send your messages based on contact availability. Other improvements include location sharing via the embedding of Google Maps links as well as support for animated GIFs.
Besides Hnagouts, Google also provides Google Voice service which works as a portable phone number and SMS service. Unfortunately Google released no information regarding any plans to combine both Google Hangouts and Google Voice into one service.