1. A method, implemented by one or more computing devices, comprising: receiving, by the one or more computing devices, an alert indicating a condition or event associated with a user device, the alert identifying a location of the user device; identifying a particular aerial imaging device, from a plurality of aerial imaging devices, as an aerial imaging device that is capable of capturing an aerial image associated with the location of the user device; requesting, by the one or more computing devices and from the particular aerial imaging device, the aerial image associated with the location of the user device; receiving, by the one or more computing devices, the requested aerial image; and responding, by the one or more computing devices, to the alert based on the received image.