wxWidgets - wxWidgets: Cross-Platform GUI Library
Zappar - Zappar is a clever little app that can see and recognise images and objects in the world around us.
Electron - Build cross platform desktop apps with web technologies
8th Wall - Cross-Platform Mobile AR
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Geocaching - Geocaching is the premier app for locating geocaches. This app is available for both the Android and iOS platforms, and it makes locating these popular hidden treasures easy and fun.