I claim the ornamental design for a blood pressure monitor, as shown and described.
FIG. 1 is a front elevational view of a blood pressure monitor showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a perspective view thereof.
The broken lines in the drawing views are included for the purpose of illustrating portions of the blood pressure monitor that form no part of the claimed design.