Something else to be concerned with is that the voltage spike of the empeg powering up (or down) has been known to set off some car alarms which are sensitive to that sort of thing. But otherwise, I like that idea.

My car's keyless-entry system activates the dome light, and I could conceive of a system where one could wire a relay to the dome light for the purpose of remotely activating the wireless unit and the empeg all at once.

But before you go to all that trouble, consider that it's still best to take the player indoors with you for a variety of reasons.