MapSDK is fully functional mobile GIS, with map and navigation API. MapSDK is written in C++, initially for Windows/ Windows CE/ Mobile. MapSDK still used in various products of big corporations around the World. If you use some Leica Geosystems devices with AutoCAD support, likely it has MapSDK inside.
We released part of MapSDK drawing engine as open-source at Github: xdraw
You might want to check out our other products:
Recognized and trusted transparent AES encryption for SQLite, since 2006
The best Vietnam stock market realtime intraday data source