One or more computing devices for presenting information to a user about a physical environment, comprising: hardware logic circuitry, the hardware logic circuitry corresponding to: (a) one or more hardware processors that perform operations by executing machine-readable instructions stored in a memory, and/or (b) one or more other hardware logic components that perform the operations using a task-specific collection of logic gates, the operations including: receiving object-selection information, in response to interaction by the user with an input device, and/or in response to preconfigured setting information, the object-selection information specifying one or more objects-of-interest, said one or more objects-of-interest corresponding to a subset of objects within a master set of selectable objects; receiving environment input information that represents the physical environment from at least one environment-sensing device, the physical environment corresponding to a physical setting in which the user uses a virtual reality device to interact with a virtual environment that occludes the user's view of the physical environment; analyzing the environment input information using a scene analysis component to determine whether any of said one or more objects-of-interest are present in the physical environment at a current time, said analyzing producing, upon an affirmative determination result, output information which identifies at least one detected object; generating alert information that identifies presence of said at least one detected object; receiving alert-condition information which specifies at least one condition in which the alert information is to be provided to the user; wherein the alert-condition information specifies that alert information is to be provided to the user only when the user is performing a prescribed action and/or when the user exhibits a prescribed state; wherein the prescribed action and/or the prescribed state exhibited by the user pertains to a manner in which the user is currently using at least one controller to interact with the virtual environment; wherein the manner comprises at least one of: the current position and/or orientation of the controller in the physical environment, the current movement of the controller, and the proximity of the controller to detected objects in the physical environment; and presenting the alert information to an output device of the virtual reality device while the user interacts with the virtual environment provided by the virtual reality device. receiving object-selection information, in response to interaction by the user with an input device, and/or in response to preconfigured setting information, the object-selection information specifying one or more objects-of-interest, said one or more objects-of-interest corresponding to a subset of objects within a master set of selectable objects; receiving environment input information that represents the physical environment from at least one environment-sensing device, the physical environment corresponding to a physical setting in which the user uses a virtual reality device to interact with a virtual environment that occludes the user's view of the physical environment; analyzing the environment input information using a scene analysis component to determine whether any of said one or more objects-of-interest are present in the physical environment at a current time, said analyzing producing, upon an affirmative determination result, output information which identifies at least one detected object; generating alert information that identifies presence of said at least one detected object; receiving alert-condition information which specifies at least one condition in which the alert information is to be provided to the user; wherein the alert-condition information specifies that alert information is to be provided to the user only when the user is performing a prescribed action and/or when the user exhibits a prescribed state; wherein the prescribed action and/or the prescribed state exhibited by the user pertains to a manner in which the user is currently using at least one controller to interact with the virtual environment; wherein the manner comprises at least one of: the current position and/or orientation of the controller in the physical environment, the current movement of the controller, and the proximity of the controller to detected objects in the physical environment; and presenting the alert information to an output device of the virtual reality device while the user interacts with the virtual environment provided by the virtual reality device.