G4S New Zealand provides Electronic Monitoring Services under contract to the New Zealand Department of Corrections for its Home and Community Detention Programmes. For Home Detention, G4S staff and approved subcontractors carry out installations, equipment retrieval, and fault attendances and respond to all offender violations. After installing the equipment, G4S staff are contracted to provide a 24 hours, 7 days a week monitoring service from their 24x7 monitoring centre based in Auckland, and to respond to violations and other incidents nationwide.

In addition, G4S provides alternate and manual monitoring of offenders during approved absences such as attending funerals, rehab programmes, and gradual assimilation back into society. The Community Detention programme targets offenders who have been convicted of less serious offences. It requires the offender to comply with an electronically monitored curfew imposed by the court. G4S provides retrospective daily reporting to probation officers, who are responsible for installing the equipment and dealing with issues of compliance and offender violation. G4S currently monitors over 3,000 offenders across both programmes. G4S produces all the equipment involved in the monitoring of offenders and, using its own in-house engineering, continues to develop electronic monitoring and to explore wider opportunities to expand its Radio Frequency, Voice Verification, GPS offender monitoring, and offender caseload management services throughout New Zealand and Australia.

In December 2012 G4S New Zealand was contracted to provide transdermal remote alcohol monitoring as part of a two-year pilot programme jointly managed by the ministries of Justice and Health, to the Alcohol and Other Drug Treatment Court (AODTC) based in Auckland. Subcontracting to Environmental Scientific Research (ESR), a Crown enterprise that provides the drug testing part of the contract, G4S supplies, fits, services, and monitors SCRAM Continuous Alcohol Monitoring (SCRAM CAM) bracelets to around 30 programme participants at any one time. SCRAM CAM bracelets are provided through SCRAM Systems based in Denver, which also provides data-analysis expertise and court reports to support any breach action. The programme is considered widely successful in both providing a deterrent from further alcohol consumption, and assisting in the rehabilitation of those participants with alcohol addictions. G4S field staff fit around three participants per week, mostly in rehab and community facilities. The SCRAM CAM anklet takes a precise series of readings from the skin every 30 minutes via a transdermal faceplate and fuel cell attached to the anklet with a rubberised strap. These readings are transmitted to SCRAMNET and analysis is conducted by both trained G4S NZ and SCRAM Systems analysts. Positive results are analysed and presented to the participant's case manager assigned by the court, who will discuss the findings with the participant and potentially may take breach action through the court assisted by using comprehensive high-quality reports provided by SCRAM Systems and supported by G4S. G4S enjoy excellent working relationships with the many stakeholders in the programme, including case managers, AODTC judges, ESR, and indeed the participants themselves.