The new functionality comes courtesy of an update to the Tesla iOS app and allows Model 3 owners to interface with Siri and find out whether their car is locked, where the car is located or even honk the horn or flash the lights.
One interesting note that Elektrek points out is that Siri responds to "My Car" rather than "My Tesla" or "My Model 3," so if you have multiple Teslas or you're just pompous, you might have some issues.
The voice commands work with the "Hey Siri" function, but your phone must be unlocked for them to work, and don't expect a problem-free experience right off the bat. Owners have reported that occasionally Siri gets a little confused and might not do exactly what you're asking for.
Currently, owners are not able to operate the trunk or the frunk with Siri, nor are they able to change the climate control or turn on valet mode, but knowing Tesla, it is possible that those features could come in the future.