The ornamental design for a fitnessdevice, as shown and described.
FIG. 1 is a front perspective view of a fitness device according to the present invention;
FIG. 2 is a rear perspective view of the fitness device;
FIG. 3 is a top view of the fitness device;
FIG. 4 is a front view of the fitness device;
FIG. 5 is a bottom view of the fitness device;
FIG. 6 is a rear view of the fitness device;
FIG. 7 is a left side view of the fitness device; and,
FIG. 8 is a right side view of the fitness device.
The structural features depicted by broken lines have been shown for the purpose of illustrating portions of the fitness watch that form no part of the claimed design.