Which is the easiest way to do Object Detection

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Both methods won't work for doors or people. The tabletop object detector is based on the assumption that all objects stand on a flat horizontal surface that can be used to segment the items (the tabletop). This is not the case for doors and hardly for people. The RoboEarth object recognizer is based on local image features (SURF), which means that it only works with non-deformable textured objects.

I'm not aware of any out-of-the box package for your use case, but there are components. openni_tracker is able to detect persons, opencv should provide methods for recognizing faces, and building a door detector using PCL should be fairly easy. As always, it depends on your setting, i.e. which sensors, which kinds of doors, open/closed, ...