Apparently it is illegal in Portugal, Austria and Luxembourg to have dash cams in your car and will result in large fines if caught, even if they are off or stored anywhere in your vehicle such as the glove box. Does this then also mean helmet cams will fall into the same category?
Not quite that clearcut they are illegal in Portugal. Reading this article they can still be used, it is how the footage is used may cause some legal rangling. I noticed that when I searched for the same for Austria, all the "newspaper sites" are saying illegal and fines up to £"stupid money", but when you dig deeper it is the same as Portugal. It is not the use of the camera but how you use the footage. See here.