I don't have a huge problem with having an ID card per se, but I would object to being required to carry one about my person at all times. I keep my driving licence, library ticket and bus pass in my purse along with all my other cards, and if I'm just popping to the local shop, I stick my bank card in my pocket.
But when I'm going for a walk near my house, I don't bother with any of it and often don't even take my phone*. I like being uncontactable for that hour or so, and hearing just the sounds of nature. I even get pissed off if I encounter someone having a loud phone chat while walking through the woods.
It's the digital aspect of this proposal that bothers me, and its scope for possible abuse if we ever get a government that's minded to use mass surveillance, along with the requirement to have a smartphone.
*This freaks my SIL out no end. She regards it as positively dangerous, despite me pointing out that I'm not out bagging Munros, I'm in Sussex, on the edge of a town and it's vanishingly rare for me not to encounter another human.