In a fast-growing universe of fitness apps that serve as exercise logs, Strava facilitates free-of-charge competition between users who typically don't know each other and may traverse on courses years apart from each other.

WSJ: The Last Place Lance Armstrong Can Race

Changi itself offers free city tours to passengers with a stopover of five hours or more but visitors can also leave the airport to traverse the city on their own accord.

CNN: Singapore stopover: Make the most of your travel time