Android: SDK, NDK, Services, Fragments, Broadcast receivers, Content providers, Custom UI components, Animations, GPS, Sensors, Localization, Tablet adaptation, Build flavours, ProGuard, etc.
Core Technologies: SQLite, RESTful API, HTTP, SSL, Websockets, HTML, XML, JSON, ProtoBuf
Third Party SDKs and libs: Facebook, Twitter, Google+, VK, Instagram, Foursquare, Flurry, Google Analitycs, Google Maps, Google Places, Fresco, Picasso, UniversalImageLoader, Android Annotations, okHttp, Retrofit, JavaRX, Sinch, Stripe, External GUI libs, etc.
Build Tools: Gradle, Maven
IDE: Android Studio, Eclipse, Xcode
VCS: Git, SVN
Tracking Systems: Redmine, YouTrack, Trello
OS: Windows, MacOS
Methodologies: Agile, Kanban
Other: Design patterns, UI Guidelines, СI (TeamCity), iOS SDK, Objective C