The ornamental design for smart keys for vehicles, as shown and described.
1. Smart key for vehicles
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
1.8 : Reference
The claimed design is an artificial intelligence smart key for vehicles that is connected to docking stations in a vehicle or at home, and displays home or vehicles information on the top display; reproduction 1.8 is a reference view showing a state of use in which a smart key is connected to a docking station; the broken lines showing of portions of the article and the docking station in reproduction 1.8 form no part of the claimed design.