If you put the nRF51822 in a weak magnetic field nothing will happen. If you put nRF51 in a strong magnetic field it will reset. If you put nRF51 in an extreme metal field it will break.
There are tests that can be done, what are your concerns?
Unfortunately I have not met this kind of case before, I'd advise to set up a testbench as see how it performs. Take the magnets you intend to use, and glue/tape them to the development kit and see what happens, if the device is able to keep turned on, i.e. not constantly resetting, you should investigate the signal characteristics with a spectrum analyzer. High H-fields from the magnets could cause disturbance in the RF-modulation and transmission characteristics.
Unfortunately I have not met this kind of case before, I'd advise to set up a testbench as see how it performs. Take the magnets you intend to use, and glue/tape them to the development kit and see what happens, if the device is able to keep turned on, i.e. not constantly resetting, you should investigate the signal characteristics with a spectrum analyzer. High H-fields from the magnets could cause disturbance in the RF-modulation and transmission characteristics.
