We make WhirlyGlobe-Maply a high performance geospatial display toolkit for iOS and Android. It's fast, it's pretty, it's a lot less work than writing it yourself.
We also make WhirlyViz a geospatial data visualization engine for mobile devices. It's for pretty maps, globes, and interactive displays. We license it for use in other apps
We do consulting based on both of these. This can be anything from full app development to new features to integration with your existing app. Contact us for details.