In a vehicle occupant response system, a vehicle navigation system supplies a vehicle location information to a computer which formulates messages for SMS transmission by a cellular telephone device. The messages are relayed by a GSM network to an Internet server. The server identifies a user account, for example from the telephone number of the device embedded in each message. The server then runs an application which is specific to a user which may comprise sending messages containing desired information to the vehicle and making available the current location of the vehicle to a user of a personal computer.