One of Ms Yap Wai Leng's twin sons studies in Australia and the other stays in a university hostel here, but she is always aware of their whereabouts.

That is because the 52-year-old IT professional uses tracking app Find My Friends on her smartphone to keep herself updated on her 23-year-old sons' locations.

"Sometimes, when I miss them, I use the app to check where they are and, if they're at a place with Wi-Fi, I can Skype call them," says Ms Yap, whose entire family uses the app.

Her husband Francis Lam, 54, also works in IT. They have another daughter, a 22-year-old undergraduate, who lives with them.

They are among a number of Singaporeans who are using tracking apps in their everyday lives, with many citing safety and convenience as key reasons.

The use of a tracking app was highlighted in a rape case heard recently in the High Court, in which the victim was found by her boyfriend at the alleged rapist's house. The boyfriend had used the Find My iPhone app to locate her after failing to reach her.

Most tracking apps work only when the user gives consent to share his location with other users. Both parties have to turn on their phones' location services for the tracking to work.

For the last four years, Ms Yap and Mr Lam have been using Find My Friends to locate their children.

Mr Lam, who introduced the app to his family, says: "I like to know where they are because then I'd know they're safe. It's not so much about having to know where they are all the time.

"At least I know they're safe without having to be very intrusive - I don't call them when they're in class or with friends."

Other users of tracking apps say they do so out of convenience.

Business undergraduate Ranice Lim, 22, says Find My Friends comes in handy when she meets her boyfriend.

"I don't have to call him to check whether he's arriving, which can be dangerous when he's driving. I can just check his location," she says. She has been using the app with her boyfriend Darrin Loh, also a 22-year-old undergraduate, for about a year.

However, she does not know many people who use tracking apps, adding that she is the only one among her friends to do so.

She feels that people are in general wary of the "negative connotations" associated with tracking others.

"It's not that I don't trust him. We don't use the app to stalk each other. It's just for the convenience," she says.

When Ms Cannie Leong's 13-yearold son started taking public transport to and from school on his own last year, she and her husband used tracking app Life360, which she says is a convenient way for them to make sure he reaches his destinations safely.

"We had told him to text us when he reached school or home, but he often forgot," says the 42-year-old administration executive.

They no longer use the app as he is now used to taking public transport.

Ms Leong adds: "He doesn't say it, but somewhere down the line, he might not be happy with me tracking him."

Ms Yap's daughter, Ms Rachel Lam, says that, at times, she does question the use of the tracking app. "It's just that, sometimes, I get the feeling I'm being watched," she adds.

This is not an issue for Ms Lauw Xiu Yu, 29, who says she is used to informing her mother about her whereabouts every day.

In fact, she introduced the iSharing app to her mother to save them the hassle of going back and forth over her location.

"When my mum doesn't know where I am, she worries. And if I don't answer her messages quick enough, she'll wonder why I'm not responding," says the customer service officer.

"So I figured that by installing this app on her phone, she doesn't have to worry and I don't have to report to her all the time."

Her mother also uses the app with her elder sister.

"Sometimes, when she's bored, she goes in and out of the app to see where we are," says Ms Lauw.

"It's like how people check Instagram and Facebook, but my mum checks iSharing."

However, she notes that this will not work with all families.

"It could turn out to be unhealthyif you get obsessed with tracking the other person's location. You have to know when to let go and hold back."