XCodeClub.com - Rent your own private Virtual Mac with latest XCode.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
VirtualMacOSX.com - vmOSX -- is your affordable, Mac-based home on the web.
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
MacinCloud - MacinCloud is a Mac cloud platform that provides on-demand Mac cloud servers, flexible dev workload infrastructure and comprehensive Mac in the Cloud solutions
Kodular - Much more than a modern app creator without coding