When Block product designer Cynthia Chen first dreamed up the idea of an app that could catalogue dogs spotted in the wild, she shelved it. "The hurdle was so big, so I never did anything," she said.

A new dating app for dog lovers, Frolly, is winning attention abroad. It is not officially available in India yet, but its concept is gaining global buzz.

Rover bills itself as the most popular pet-sitting app in the U.S., with tens of millions of bookings since the service was founded in 2011. But just like other gig-economy apps such as Uber and ...