Kill switches 'cut thefts' in London, New York and San Francisco

The addition of "kill switch" anti-theft tools to iPhones and Android handsets appears to be acting as a major deterrent to criminals.

London, New York and San Francisco have all announced major drops in the number of reported stolen smartphones since the facilities were added.

A kill switch allows an owner of a stolen phone to send a command that blocks it from being accessed or reset until an ID and passcode are entered.

Microsoft has yet to add the feature.

Apple was first to introduce the measure. It included Activation Lock as an option in its iOS 7 operating system in September 2013.

The latest statistics for the two US cities are based on a two-year period running from the start of 2013 to the end of 2014:

London presented its numbers slightly differently, comparing the 12 months leading up to October 2013 with the same period the following year.

It reported a 40% drop in smartphone thefts and a 38% fall in robberies of smartphones involving violence or the threat of violence.

The figures from England's capital also indicate that since Apple introduced its kill switch:

The three cities created the Secure Our Smartphones (SOS) initiative in 2013 to pressure smartphone manufacturers and mobile networks to help tackle smartphone thefts, after experiencing spikes in related crime.

"We have made real progress in tackling the smartphone theft epidemic that was affecting many major cities just two years ago," said London Mayor Boris Johnson following the latest announcement.

San Francisco District Attorney George Gascon added: "Preventing their own customers from being the target of a violent crime is the coolest technology [the mobile industry] can bring to market."

The authorities are still pressing for further change.

Although Apple made its kill switch the default setting on new iPhones running iOS 8 - meaning users do not need to switch it on, but rather must switch it off if they do not want it - this is not the case for other devices.

So, while Google announced in October that its Android Lollipop operating system would introduce an opt-in feature called Factory Reset Protection, it is not currently offered by all handsets running the system.

Likewise, Samsung's proprietary Reactivation Lock facility, offered on some of its Galaxy S5 smartphones, must also be turned on manually.

The SOS initiative, however, is calling for kill switches to be automatically activated on every mobile device.

"A default solution is imperative because it ensures all device are worthless to thieves," a campaign leaders said.

Microsoft has promised to incorporate a kill switch into its smartphone version of Windows 10, but has yet to announce when the OS will be released.

Smartphone chip maker Qualcomm has also announced a hardware-based kill switch facility, to be called SafeSwitch, that it will offer to manufacturers that use its latest processors.

The firm describes this as a "superior solution" to others' software-based efforts.

But handset-makers have yet to say if they will make the facility available to consumers.