The Apptentive SDK gives you a simple but powerful channel to communicate with your customers. With it, you can manage your app's ratings, let your customers give you feedback, respond to customer feedback, show surveys at specific points within your app, and more.
Events and Interactions - Keep track of customer behavior, and initiate conversations with each customer based on their behavior. Interactions are the UI elements that you use to interact with each customer, and Events are records of past customer behavior.
Ratings Prompt - The Ratings Prompt Interaction is a powerful tool to help you get better ratings and more reviews from happy customers, and start conversations with customers who have feedback, suggestions, or critiques. The Ratings Prompt is a series of views. The initial view is called the Enjoyment Dialog, and ask the customer whether they love your app. If the answer is yes, then they are shown the Rating Dialog, which offers them the opportunity to go to the app store to rate the app. If they don't love your app, they will be taken to the Message Center where they can give you feedback.
Surveys - Surveys are Interactions that help you understand the wants and needs of your customers. Surveys are composed of one or more questions, and since they are Interactions, can be targeted to any Event you have configured in your app. There are three supported question types: Single Select, Multiple Select, and Free Form.
Upgrade Messages - Many customers choose to have their apps automatically update. While this is convenient for them, it mean they often won't see announcements or release notes that you display on your app store page. Upgrade Messages solve this problem. You can configure an Upgrade Message for each release of your app. When the user upgrades from a previous version of your app to one of the targeted versions, whey will see the Upgrade Message.
Message Center - With the Apptentive Message Center you and your customers talk directly without making them leave your app. Handling support inside the app will increase the number of support messages received and ensure a better customer experience.
Smack is an Open Source XMPP (Jabber) client library for instant messaging and presence
If only they added Unity Support
They have great support and very needed product- get rate requests and surveys via the app. It's relatively an easy development but if your devs are loaded, it's a quick SDK setup and you've got a rate us in app mechanism.