A driver-initiated warning device is described for communicating descriptive vehicle-to-vehicle warning messages. The device can be deployed within an automobile and can include an interface that receives input from a driver or passenger of a vehicle. The device also includes a vehicle-to-vehicle communications component that generates anonymous messages upon having received the input and broadcasts the anonymous messages to other vehicles within range. The anonymous messages have embedded electronic data regarding an event observed by the driver or passenger, such as location information of a road hazard. Based on receiving the messages, the device can make decisions as to whether to alert the driver of any upcoming dangers or other events. The location information contained in the messages can be used to filter the messages based on relevance. The messages can also be relayed to other vehicles in order to optimize information diffusion between moving automobiles.