A memory stores a message map associating requests with human-machine interface (HMI) notifications. A vehicle receives a request from a secondary-connected device, and sends an HMI notification to a primary-connected device, constructed based on the message map and the request, to simulate user input to the vehicle to cause the primary-connected device to perform the request. A secondary-connected device connected to a vehicle computing platform receives a command, constructs a request message describing the command; and sends the request message to the computing platform, to cause the computing platform to send a HMI notification to a primary-connected device to simulate user input to the vehicle requesting the primary-connected device to perform the command.