Available immediately from Russell's website, the panel is described in detail in a QuickTime tutorial video. The panel allows overlay of either text or graphic watermarks on either all open images, or on a specific folder of images. The overlay graphics can be in JPEG, PNG, TIF, Adobe Illustrator (AI), and Adobe Photoshop Document (PSD), including images with transparencies and blending where supported by the file type.
The watermark can be positioned relative to the corner or edge centers of each image, with control over both transparency and positioning in pixel / metric / imperial units. Resulting JPEG images can be automatically scaled or sharpened before saving, and the controls allow for adjustment of both JPEG quality and dpi resolution.
More details -- including the 800KB installer download -- can be found on Russell Brown's website.