Suntimes - Android app (and widget collection) that displays sunlight and moonlight times for a given location.
Solaris Sky Calendar - An astronomy calendar right in your pocket
SunCalc - Find out where the sun will be at any time in any location
GoldenHour.One - Your personal assistant for outdoor photography for iOS
Sol: Sun Clock - Get reminded when it's sunrise or sunset, wherever you travel!
Alpenglow - Never miss a incredible looking sunrise or sunset again