A Bluetooth enabled Smartphone may be used for both access control and start authorization in a secure and safe way, and embodiments are backward-compatible with conventional vehicle access and start systems. A smart phone acts as an intermediary authorization device to a code generator which effectively resembles a car key that is installed in a vehicle. A Bluetooth transceiver and the code generator—and, optionally, for the retrofit solution, an RF/LF transceiver—are added to the vehicle. The Bluetooth transceiver communicates with the smart phone. The code generator communicates with electronic control units in the vehicle that control access, immobilization, and engine start. The communication may happen via a wired connection or, in the case of the retrofit solution, via an RF/LF transceiver that mimics an additional car key programmed to the vehicle.