imo was originally a messaging app that could manage a lot of different social networks and chat apps. It discontinued support for third party messaging in March 2014 and reemerged as a standalone app, offering the same features as other messaging apps.
Standard feature set
imo offers chat, video and voice calling, group chats, and photo sharing. These features are standard for most messaging apps except imo is locked in its own platform so friends and family will have to join.
The app is cross platform so you can log into the service on Amazon, Android, and iOS devices. It is also available on web browsers.
When chatting, imo secures your chats with SSL/TLS and video calls are encrypted, according to imo.
Another messaging app
Voice and video calls can work over cellular data or Wi-Fi so you can always make calls if necessary, but you will have to watch your carrier data caps.
Not worth adding another app
Since its change, imo is another chat app looking for an audience. Its usefulness was removed in 2014 when it stopped supporting third-party chat. Now it's trying to find a place in the saturated messaging market with competitors that are offering the same features with a larger audience.