Google has been trying to come up with some sort of way to create a system similar to iMessage, and for awhile, the RCS project was going to be that; however, it was left up to carriers to implement, and apparently, they’ve failed miserably.
Phones still operate primarily over SMS and MMS, whereas Rich Communication Services (RCS) was supposed to replace those two methods. Nearly a decade in development, almost nothing has happened there.
So now, the Search giant is taking on the project, and will be uploading the RCS protocol to their servers for their fairly new Messages app.
This would be nice because RCS would be available pretty much everywhere, working more like iMessage than being carrier-specific.
The biggest problem is concerns over privacy — the major thing that RCS lacks is end-to-end encryption, so Google could — in theory — keep or store your conversations.
Either way, this is a big move towards RCS adoption. For the time being, it’s only going to be available in France in the UK, but Google will roll it out to other countries over time.