Hmm. Interesting question. I'd kinda wonder that particularly with anything that stores data. I've had credit cards wiped by magnets, and that was how we used to wipe hard drives when I worked in IT. Flash memory may be different, though.
That said, I've carried my phone and tablet in a magnetic tank bag for a long time, and never had a problem. Not saying you won't, but I haven't.
That said, I've carried my phone and tablet in a magnetic tank bag for a long time, and never had a problem. Not saying you won't, but I haven't.