A portable electronic device, like a cellular telephone is capable of detecting collisions between vehicles and notifying the proper authorities. The device includes a microprocessor and memory, in addition to an accelerometer and global positioning systems receiver. The memory includes at least one filter for screening out false positives, which are false collision detections. In one embodiment, the device determines its velocity. It then checks to see if its velocity falls within a range associated with moving vehicles. If so, the device monitors the accelerometer. When acceleration values in excess of a predetermined threshold are detected, the device pauses and again checks its velocity. If the velocity has fallen from the range associated with moving vehicles to a range associated with a vehicle that has sustained a collision, the device notifies emergency personnel that a collision has occurred. Another filter includes an operability check of the keypad, coupled with a notification message that the authorities will be called if the keypad has not been actuated within a predetermined time. Another embodiment includes a detector capable of detecting a vehicular cradle, such that the notification only occurs when high acceleration values are detected in a vehicle.