In an ideal world there would be one application that could be used on phones, tablets and computers that allow for seamless communication and notification across devices. This is where the rumoured 'Babel' app comes in. The internet has been abuzz with leaks and information about the service with even some possible screenshots a couple weeks ago.
In my opinion it looks like the chat window that pops up when you use Google+ on the web. It also looks like it would be easily transferrable to a mobile environment. I like how clean it is and absolutely love the card based interface that has been going on with Google design.
The rumour is that at launch everything will be rolled up into one application except for Voice and SMS/MMS. This is a big win for Google, having everything rolled up and working together, I wish they had been able to roll SMS/MMS into the application at launch and of course with no official announcement yet it could still be included. This would be an important addition in order to compete with both iMessage and WhatsApp and would make using it that much easier.
Another feature I would like to see from it is taken directly from BBM and that is read receipts. I don't really know what difference they would make but I do like the idea of it. I also like the idea of integrating service that I use with all of the Google Apps that I use.
Interestingly enough a commenter in The Verge forums may have given the best information we have about the new service. In the forum he states that the service would be called Hangouts, and will not include SMS and have a full Holo design. These are pretty safe bets in general but for the non-believers out there this specific commenter also gave accurate information about the launch of the Nexus 4 and 10 in the fall leading to some credibility behind the story.
I truly can't wait for this to be announced at I/O in a week and hope it catches on to beat out the many many competitors that are out there. I have a big hope that there will be some way for it to work on all of the major platforms as I still have friends that use Blackberry or Windows Phone and if I could use it with them it would be a very big deal.
Once again I cannot wait for I/O to see what surprises Google has in store for us, and it still makes me wish that I had friends inside Google that would let me play with things before they were announced.