Google's Allo messaging app is out, and its "killer feature" is the Google Assistant which you can bring into the conversation as needed. For example, I could have called in the assistant to provide suggestions when I was planning a wing night with some friends yesterday. Instead, I had to exit the chat, find the restaurant and then paste it back into the chat.
The internet had hoped that Allo would be like Apple's messaging system - it sends data messages to people also using the app but reverts to SMS for others - but this isn't the case. It's a closed system like Facebook Messenger or WhatsApp. So, its success will depend on getting enough of your friends to use it.
A lot of people will say "without SMS and a desktop client it's DOA", but let's not forget that we're heading towards a mobile-only world that doesn't use SMS. The developing world is already there and our North American preferences are the outlier. But, it will still depend on getting a critical mass of users. That's where this app will succeed or fail.
The beauty of the smartphone is that you can have all the apps, so if you want to reach me on Allo feel free to contact me that way. But I'm also on WhatsApp and Facebook Messenger and Hangouts. I'm not going to limit myself because I really don't have to.
If no one decides to switch I can still talk to the assistant, of course.