The ornamental design for a wall mounted touchscreen, as shown and described.
FIG. 1 is a front view of the wall mounted touch screen of the present invention;
FIG. 2 is a right side view of the wall mounted touch screen of FIG. 1;
FIG. 3 is a left side view of the wall mounted touch screen of FIG. 1;
FIG. 4 is a top view of the wall mounted touch screen of FIG. 1;
FIG. 5 is a rear view of the wall mounted touch screen of FIG. 1; and,
FIG. 6 is a perspective view of the wall mounted touch screen of FIG. 1.
The broken line showing of structural features is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.