netTerrain Logical - Automated network documentation & drawing tool
rmtoo - rmtoo is a free and open source requirements management tool.
Prolaborate - Collaboration software for Sparx Enterprise Architect
Doorstop - Requirements management using version control.
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Requirements Quality Suite - The Systems Engineering Suite offers you the tools, processes and skills to Verification, Traceability, Reusability and Quality.