Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Fuse - Fuse is a UX tool suite for mobile app designers and developers.
Qt Creator - Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment. It is the fastest, easiest and most fun experience a C++ developer could wish for.
Dropsource - Mobile development platform for building native iOS & Android apps
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.
GoodBarber - GoodBarber is a mobile app creation platform.