When he was still married, John(not his real name) would receive a daily call at 6pm from his ex-wife at work.

Sometimes, she even turned up unannounced at his office just to "make sure I wasn't off meeting people I wasn't supposed to", the 37-year-old public relations consultant tells The New Paper on Sunday.

Was she being unreasonable? And how far is too far when it comes to insecurity in a marriage?

John's ex-wife was not alone in her efforts to keep herman on a tight leash.

Private investigators (PIs) tell TNPS that John's case is mild compared to other methods they know of.

These days, they say, husbands or wives turn to technology to track their spouses.

They will usually urge their other halves to subscribe to apps like the iPhone's Find My Friends, which allows you to locate friends who have also signed up for it.

Such services work by using the phone's global positioning system (GPS) to pinpoint the user's exact location.

But it is not always reliable, says Mr Lawrence Koh, 43, the managing director of SK Investigation Services.

He explains: "Such tracking services can only estimate the subject's location. Furthermore, it would not work if the phone's GPS system is de-activated."

John, who spoke on the condition of anonymity, claims he was never unfaithful during his two years of marriage.

He did not want to be named to protect his ex-wife's identity.

"I did everything I could to convince her that I wasn't seeing anyone else, but she did not believe me," he maintains.

"In my job, I had to work late, but when I told her I had to meet clients, she would scream at me, apparently for abandoning her."

The very public fights - sometimes in his office - affected his work performance, says John.

In 2004, he was sacked from his job.

Eventually, John grew tired of living under constant surveillance.

The couple divorced in 2005.

Mr Koh says he has seen many suspicious spouses turn to PIs todoa more "complete job of investigating".

But this does not come cheap as they may have to fork out up to $5,000 for a week's work.

"Interestingly, I'm seeing more male clients turn to us. Ten years ago, we had more women coming to us to trail their spouses," says Mr Koh, who has been a PI since 1988.

"Once, we had this man requesting that we plant a GPS device in his wife's car to track her whereabouts.

"But we could not do it because he was not the owner of the vehicle. Also, we would be in trouble with the law for invading his wife's privacy," he explains.

Employing professionals to do your tracking is costly.

The alternative, one housewife says, is to employ her husband's family members and friends to spy on him.

"It's cheaper, too," says Mrs Rohaidah Ali with a laugh.

Two years ago, the 39-year-old suspected her husband of 10 years, a sales manager, of cheating on her.

She called his friends to track his whereabouts.

"I even called his office pretending to be from another company to find out why he was working nights so often," she recalls.

"Calling up the office was tricky, but his friends and family members were helpful because they were concerned about my marriage," she says.

"I was very relieved to learn that he wasn't cheating on me. He was just distracted by work.

"Looking back, maybe it wasn't so nice to spy on him, but I was just protecting my marriage. That was my concern."

This article was first published in The New Paper.

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