Simple maps app that displays maps based on OpenStreetmap like MTBMaps, Hike and Bike Map and Carto DB and can import gpx files.
Retina maps are used where available. https://github.com/hyperoslo/Cache is used for caching. The app is available on the AppStore
Join the Testflight group for occasional betas here: https://testflight.apple.com/join/6vHqOfhG