Finding a lost or stolen Mac works even when the machine is sleeping …
In sleep mode, it can still send low-energy Bluetooth signals which can be picked up by any other Apple device within range. So if there is anyone at all with an iPhone, iPad or Mac within Bluetooth range of the Mac, it will relay its location back to you.
All data is encrypted and secure, so that none of the other devices relaying the data will have access to the location, and the feature has been designed to use minimal data and battery power, so it has negligible impact on the relay devices.
Apple has also added Activation Lock to the Mac, which works with any Mac with a T2 chip. As with the iPhone and iPad, it will make a stolen Mac useless to anyone else, as it can’t be wiped without your Apple ID.
As with iOS devices, Macs may still be stolen for parts, but it will make Macs dramatically less appealing to most thieves.
9to5Mac exclusively revealed the unified app plans back in April.