It’s an urban myth. I have kept my phone inside the main bag with no issues. Magnets don’t affect phones or tablets - an iPad has magnets in it to attach covers etc. however, if yo are still worried, There is a lid pocket inside, and another mesh pocket in the divider - away from any tank magnets.I have just bought and fitted a SW-Motech PRO City WP tank bag, I thought it may be a good place to stash my smart phone and run a lead from the USB socket to charge the phone as I ride, but I have heard that I shouldn’t put a mobile phone in there because of the magnets used to attach the bag.
Any truth in this or is it just another urban myth?