Photo Pixelizer covers sensitive details in photos, such as faces, unwanted advertising or brands, etc. Sensitive areas can be covered with solid color, a professional looking pixilate effect, or by bluring (full resolution supported for all types).
Faces can be automatically detected and covered (by using the menu entry "Face detector").
The full version is available here: https://play.google.com/store/apps/details?id=com.teapps.photopixelizer