In one aspect, a system for monitoring the condition of a seedbed within a field may include an implement having a plurality of ground-engaging tools supported by the frame, with the implement being configured to create or be traversed across a seedbed extending downwardly within the field from an outer seedbed surface to a seedbed floor. The system may also include an auxiliary support arm coupled to a portion of the frame at or adjacent to the aft end of the frame. In addition, the system may include a seedbed floor detection assembly coupled to the auxiliary support arm that is configured to detect variations in a profile of the seedbed floor. Moreover, the system may include a seedbed surface detection assembly coupled to the auxiliary support arm that is configured to detect variations in a profile of the outer seedbed surface.