One of them calls to inquire about swing-dancing lessons; another asks if he can spend half an hour in a $2 shop: one feels like killing again.

Some ring to say they are late for the 501 bus to Bi-Low, others report they are having a heart attack.

On the other end of the phone are the people who watch them – 24 hours a day.

When the state's worst sex and violent offenders finish doing time for their crimes, they are released into society.

But some are at such high risk of committing the same offences that an application is made to invade what amounts to every moment of their lives.

There are 37 people living in NSW being watched on extended supervision orders.

These orders allow Corrective Services NSW to tag, monitor, counsel and visit them around the clock until they are capable of living on their own.

The orders are granted by the Supreme Court of NSW and force criminals to comply with the strictest of conditions on the outside.

If imposed conditions are breached, offenders can be sent back to jail for up to five years.

Assistant Commissioner of Community Corrections, Rosemary Caruana, said the alternative to these orders is releasing an offender into the community with no supervision at all.

"The alternative would be nothing. If we didn't have this legislation, they would be out there … no supervising, no monitoring, no accountability – they would be out there now," she said.

"They don't like it … The offender comes into this on the basis that they have done their crime, they have done their time and they see this as penalty."

Offenders have to submit a schedule of their movements and stick to it down to the minute.

For example, a paedophile must ring his officer and tell them the time of the train they are catching to see their forensic psychologist and then how long they want to spend in the park on the way home.

"They step out of the wrong area, they get a phone call saying, 'what are you doing there?'," Caruana said.

Among the 37 men under supervision are –

Colin John Fisk: Paedophile, released in May 2009 after serving 12 years. He told the court he was rarely aroused watching SBS films but occasionally had sexual fantasies about his victims.

John Alan Wilde: Serial rapist, served 28 years. In 1991 he stabbed and assaulted a woman while on parole. Filed to have midnight curfew lifted last year – he wanted to stay out with the Christian motorcycle group, God's Squad.

Raymond Cornwell: High-risk sex offender who violently assaulted five women over a two-year period. After being released in 2007, he cut off his ankle bracelet. Two years later he breached conditions drinking alcohol. He was due for release last month but the Attorney-General made a detention order.

Terry John Williamson: Notorious Bulli rapist who bound, gagged and raped 11 women and children at knifepoint during a 10-month rampage. He was paroled after serving a 24-year sentence for 19 charges related to the sexual assault of nine women, a five-year-old girl and an 11-year-old boy.

Scott David Lynn: Parramatta shopping mall killer who removed his electronic bracelet in April last year and was on the run for a month until he was arrested in Sydney's CBD.

The people who keep an eye on such men are a combination of Corrective Services officers, psychologists and police.

Every fortnight they sit down to look over offenders' schedules and flag potential risks.

At a recent meeting, seven people met to discuss how the offenders were behaving and ways in which they could minimise the risk of them acting out.

Sydney West Community Corrections director Michelle Micallef brought the case of a convicted murderer who had informed his officer that he wanted to kill again.

"He's really good at expressing himself … he actually helps us, he is ridiculously honest," Micallef said.

The manager of the extended supervision order team Ellen McCarroll said: "We thought the homicidal thoughts would have been enough to keep him scheduled".

A debate followed about what needed to be done.

"I don't want to explain that we said nothing [if anything happens] to the Coroner's Court," said NSW Police acting Detective Superintendent Chris Goddard.

The group decide the man was an acute risk and decided he needed to have more outings planned for him.

"He needs to have some more social activities in there," McCarroll said, pointing to a space in his calendar.

The group moved on to discuss another offender, who is so compliant he called his monitoring officer instead of triple zero when he was having a stroke.

"That was quite novel," Micallef said.

The police explain they had done a recent search of his computers and had not found anything that would raise flags:  "We've not had a hurdle with him for two years; he's doing really well."

Micallef said working with police and psychologists really helped to assess the risk of each offender.

"We are doing this with a whole group of people and the outcome is clear – we are working hard to protect the community,"

"[The meetings] give you a sense of how involved we are in their lives."

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EVERY movement of a high-risk offender is tracked with a grey, 300-gram anklet lined with steel and anti-tamper plates.

The GPS signals are transmitted back to an electronic monitoring room in Sydney's Silverwater Correctional Complex.

The Smart Tag stores data and sets off alarms if the person goes into an exclusion zone, is late for their curfew or tries to remove the device.

Exclusion zones are manually set and for a paedophile could mean not being allowed to go to parks, near schools or beaches during school holidays.

Tags can also be set to go off if an offender goes anywhere near a co-accused, victim or an associate he is not allowed to talk to.

The security and intelligence manager points to a screen showing the movements of one offender.

"You can see this person – he's wandering, he's aimless," the manager said. "Anklets will tell you where they are but not who they are with or what they are doing."

Behind the manager, officers are calling offenders, asking them why they aren't home or why they are in an area deemed an exclusion zone.

"You really have to understand the offender's behaviour. I could watch a guy sit in the park all day and be fine but if he sits outside Commonwealth Bank for five minutes I'd send someone out there straight away [if he had a history of armed robbery]," the manager said.

There is a beacon in the offender's home that registers when he enters, and it reports back to the electronic monitoring room.

If offenders need to deviate from their planned schedule in any way, they have to call.

"If there is a car accident or a train delay, they have to ring in and say 'I'm going to be delayed' and then the monitoring room will check RTA websites, traffic updates and verify what they are saying."

But the tracking devices are not steel cages, they cannot stop people from being violent or acting out.

"What we can't control is him reoffending. All it takes is five minutes, five minutes to grab somebody, do the dirty, five minutes to grab a kid, five minutes to punch someone and move on," Caruana said.

"But they are adhering to the schedule and from an electronic monitoring room we can see where they are but we can't stop them from doing anything."

More than 500 new anklets were rolled out in December 2014, at a cost of  $2 million a year.

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IF an offender appears to be spiralling out of control – they are stopped pretty quickly.

There are 50 people now subject to an extended supervision order. Thirteen have been sent back to jail for breaching orders.

Breaches can include not reporting to their officer, taking drugs or alcohol, committing other offences, having child porn on their computers, not showing up for appointments or being charged with historical offences.

NSW Police became part of the Corrective Services investigation unit in February,  which means offenders can be arrested the moment they breach conditions.

Most of the offenders live  in Sydney.

Some fiercely resist scrutiny. Others prefer to remain in jail than be watched and there are a few who do not realise they will be scrutinised after serving their sentences.

Caruana said the end game was making sure the community was safe but also to help the men eventually rehabilitate.

"We are never going to eliminate risk but we can minimise it."

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Extended supervision orders

• 37 high-risk offenders living in the community on extended supervision orders (ESOs)
• 76 offenders placed on ESOs since introduction of legislation in 2006
• Only one ESO offender has been convicted of reoffending for similar offence
• 16,000 offenders on a range of orders, including home detention, bonds, parole