"It's effectively a GPS system, provided we've got coverage," he said. "Basically it's a safety device to be used by our staff as and when the need arises."
The device was used by an officer in Gisborne last month when dealing with a "violent and agitated individual" and couldn't request help on his radio because the channel was busy, Mr O'Leary said.
"As a result of using the officer safety alarm, staff responded pretty quickly."
Costing $435,156, a total of 1500 alarms were rolled out to police districts that weren't on the digital radio network in November. The devices have built-in GPS technology - finding officers' locations faster in times of emergency.
Police communications centres national manager Superintendent Andy McGregor told police's Ten One magazine that staff on the digital network already had safety features built into their radios but an up-to-date solution was needed for those in other areas.
"Radio is still the most important piece of safety equipment for officers but we want them to have the added security of another way to request urgent help," Mr McGregor said.
To request urgent assistance, an officer holds the alarm button for one second, sending a signal to the police communications centre, creating a "1E" emergency event and showing the dispatcher the officer's location.
The alarm then vibrates, letting the officer know help is on the way.
In one of the most serious scenarios in which the device has been used since the roll-out, Ten One detailed how an officer activated his alarm when he needed assistance during an arrest in an area with poor radio coverage.
"Things moved quickly and he was overpowered and assaulted. While lying on the ground in a defensive ball, he was able to press the alarm a second time. Assistance arrived soon after."
The devices operate on the 3G network, relying on GPS satellite and cellular coverage. They have also been used to pinpoint officers' whereabouts in remote locations, from dog handlers pursuing offenders off the beaten track, to sending rescue helicopters directly to crash sites.
By the numbers
6emergencies where officers sought assistance
19 events where officers used the devices to pinpoint a location
133 false alarms
111 tests
614 total activations