1. An in-vehicle system for emergency communications, the in-vehicle system comprising: a digital processor; an emergency event detector arranged to communicate with the digital processor; a GPS receiver arranged to provide location information to the digital processor; a memory coupled to the digital processor for storing program code and/or data; a wireless telecommunications module arranged for interacting with a wireless telecommunications network as a mobile terminal unit and operatively coupled to the digital processor; an in-band modem coupled to the digital processor or executable as software on the digital processor and operatively coupled to the wireless telecommunications module for transmitting data in the voice channel during a wireless voice session; and application software for controlling the in-vehicle system, the application software configured to: transmit a predetermined control signal in the voice channel responsive to establishment of the wireless voice session using the in-band modem, the predetermined control signal comprising a start data session indication that is configured to signal a call taker server to prepare to receive data transmitted in- band during the voice call session; after transmitting the predetermined control signal, determine whether the call taker service is ready to receive data on the voice channel; and responsive to determining that the call taker service is ready to receive data on the voice channel, transmit the stored program code and/or data in the wireless voice call session using the in-band modem.