After a night out with some old classmates, he decided to activate the Find My iPhone app on his wife's phone for the fun of it.
As it was late in the day, he expected that she would be at their home.
But the app displayed her location at a budget hotel in Lavender.
Such apps exposing extramarital affairs are common, said private investigator James Loh. He handles about four cases a month.
He added: "The Lavender case happened about two years ago and the client had the shock of his life.
"He staked out the hotel with his brother, and after seeing his wife there multiple times with a man, he came to me for help to gather more information on the affair."
There are hundreds of apps which use geo-location data to a high degree of accuracy.
These apps can be proprietary, like Find My iPhone and third-party ones.
Proprietary apps need to be activated while third-party apps must be downloaded.
Said Mr Loh: "If a husband buys and sets up the phone for his wife, he can pre-install these apps without her knowledge and he might have access to her passwords."
Some tracking apps
FIND MY IPHONE
The iOS app allows users to use their Apple ID to find a missing phone on a map or sound an alarm. The Lost Mode enables users to lock, track and remotely wipe all personal information from the phone.
FIND MY FRIENDS
This iOS app allows users to locate friends and family using their mobile phone by inviting them to share and follow their locations. Users can also set up location-based alerts that notify when other users arrive at a set location.
The Android and iOS app offers find-my-phone features and also scans downloaded apps for malware and backs up data on its servers.
It also allows remote wiping of data from the phone and monitors the phone's Web browser and sends alerts if users visit unsafe websites.
LIFE360 FAMILY LOCATOR
Track family members in real time using this app which is available in Android and iOS.
It can automatically let family members know when someone has entered a predefined location, like home or school, and has a built-in "panic" option that sends out an emergency beacon to designated contacts.
Tracking apps have been used to trace the location of people in danger.
Last year in the US, a mother tracked down her 18-year-old daughter who had been kidnapped by her former boyfriend.
She alerted the police who found the girl bound and gagged.
Here, in a trial which started last Thursday, the High Court heard that a woman's boyfriend used the Find My iPhone app on her cellphone to track her down when she went silent while clubbing. He later found her in an unfamiliar house after she had been allegedly abducted and raped by Ong Soon Heng, 40.
Director of DP Quest Investigation Consultancy David Ng said such apps are essential when the safety of a person is involved. "On the surface, such apps might be seen as intrusive and an invasion of privacy, but in crucial situations, one would be thankful for it."
He said parents of teenagers have used tracking apps to make sure that their children are safe.
"But it's not healthy to track teenagers, especially if they're at a rebellious stage of their lives. It's appropriate if it has to do with gang or drug-related cases and they are in serious danger."
Mr Loh said employers have also used these apps to track employees who are issued company cellphones.
On occasions when he has to tail them, he has discovered employees selling company goods illegally or using vehicles for private trips. "Sometimes the company drivers make detours or stop at unusual locations, and that's when we're called in to follow up and see what's going on."
Mr Ng said more advanced tracking apps can even record messages, pictures and personal information remotely.
"It's all about the intention of tracing the person's whereabouts," he added. "However, I believe these apps can bring about peace of mind for those looking out for their children and family so it is by and large good to have it."
National University of Singapore's Associate Professor Chang Ee- Chien, who specialises in IT and cyber security, said it is not just tracking apps that people should be wary of. Even social media check-ins can carry risks and users can unknowingly disclose too much personal and real-time information.
"People need to be educated about the risks of oversharing and documenting their movements - make sure you only share your location or tracks with trusted people," he added.
NUS Associate Professor Roland Yap, however, said it is now near impossible not to be tracked as long as you use a mobile phone.
"Your mobile phone provider can track you through the network or someone can use GPS to find out your location.
"The only way to stay off the grid is to use a disposable phone, or simply turn off your phone."
He added: "As Facebook founder Mark Zuckerberg once said, and I'm paraphrasing, 'Privacy is dead'."