Hippomap is the subway and rail map of the world. They provide a 3-touch interface for subway and rail travelers to access map information, including subway / rail / high speed train maps, as well as local maps. They launched their test product (Hippometro) on iOS and they are working on their coverage, offline backup maps, and Twitter feeds.
Their next phase is called Stationmaster where local users will recommend the best restaurant, art venues, shops, etc in their neighborhoods to travelers. They have maps for cities across Asia, Europe, Africa, North American Oceania, and South America.
Trains and subways are some of the most convenient means of public transport, and a map that shows all of them around the world on one easy-to-use platform is an incredible tool for any geographic explorer!