Guys, I've been searching for a something that does the job for 2 years now. Found something and it works !!!!
https://www.amazon.co.uk/FIREFLY-Sm...&qid=1508525274&sr=8-2&keywords=tunai+firefly
Tiny device which plugs into the USB for power and the Aux for playing music. When the engine is switched off, it also switches itself off after a while, so no risk of flat battery. NOTE - there seems to be something they have to do to tweak it for older Maserati's (mine is 2009 Granturismo). First one they sent works on newer car, but not on Maserati - then they sent a second tweaked one, which is fantastic. Just stays in the glovebox plugged in and works a dream. So I'd suggest mentioning this very specifically when you order.
End result - get into the car - bluetooth connection from iPhone to just start streaming music. Very pleased indeed.