An activity recognition device comprises a port configured to receive a video stream from a video source for a first object and a second object; a memory configured to store instructions and image frames of the video stream; and one or more processors, wherein the one or more processors execute the instructions stored in the memory, the one or more processors configured to: select portions of the image frames based on presence of the first object; determine areas within the portions of image frames, wherein locations of the first object in the video frames are bounded by the determined areas; determine motion of the first object and locations of a second object within the areas of the image frames; and identify an activity according to the determined motion and locations of the second object, and generate an alert according to the identified activity.