The BMW free Apple Watch app is available on Apple's iTunes store.
BMW says the new technology allows the driver to be connected with their i3 or i8 at any time — "remotely, if required, and allows users to check or control important functions directly via BMW i Remote app, without having to take their smartphone out of their pocket, unlock a screen or enter a code."
It added that smartwatches will make "using electric mobility a faster and more direct experience."
Apple Watch uses the BMW i Remote app to keep users updated on the car's current battery status, for example, and then alert them when the high-voltage unit is fully charged.
The Apple Watch can continue the navigation instructions every step of the way from the BMW i3 to the user's final destination after the car has been parked and guide them back to the car, if required.
The interior temperature of the cars can be set through the watch.
Porsche said drivers can now access Porsche Car Connect functions from the watch.
"The Apple Watch provides information on the vehicle status and allows certain vehicle functions to be monitored and controlled by tap and gesture input," Porsche said in a statement.
The car can be locked remotely and drivers can be guided to their car in a crowded parking structure.
Edmunds says: Expect other automakers to follow Porsche and BMW in this high-tech effort.