The ornamental design for a smartwatch, as shown and described.
1. Smart watch
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
1.8 : Another front view
The broken lines depict portions of the smart watch that form no part of the claimed design; the dash-dot broken lines define the bounds of the claimed design and form no part thereof.