London-based Pusher supports mobile application development with pub/sub messaging and "presence channel" which supports discovery of live users of applications as well as messaging or chat room capabilities to applications, and finally location services as well (e.g. geolocation).
1. It's open source which supports range of languages, operating systems and languages. Well suited for Android and IOS mobile automation. Supports all kinds of apps, which makes it flexible and robust mobile testing tool 2. It is less appropriate where we need intercept network call to verify the API calls. Extensive coding experience is required to work Appium
As I told you earlier, if you just want to send regular push notifications to the app users, then Pusher shall not be your first choice. However, if you wish to make the app a little more interactive by making live changes in the app using Pusher and sending your user's real-time notifications, then you should definitely try it.
If you're an Apple developer, you use Xcode. It's practically a forced necessity. For system testing though, it doesn't have to be. You can have your development team focus on unit and integration tests in their platform and another team automate acceptance tests with a language they are more familiar with.