As explained in your safety briefing what you can bring aboard the helicopter for the duration of your ride is only essentials that would be allowed, as everything else will need to be left behind.
So all photography devices such as your digital camera and phone will be allowed, providing the flash is switched off.
You can bring sunglasses but you don't have to wear them, so make sure you have pockets as to avoid carrying them the entire trip.
Under certain circumstances a hat to stay warm will be allowed, but avoid bringing gloves or a scarf as accessories such as this can cause a nuisance around the chopper.