I have build a food zappicator many years ago. I just wanted to build one as a good made item, in robust housing, etc. not as a real working device, thus never used it. I found it recently and decided to measure with my EMF meter if it radiates anything at all (what is measurable). Of course there is static magnetic field, which isn't interesting in this case, as it is normal for each magnet. AC or pulsed magnetic field is not generated, or at least it is not distinguishable from the background MF of the house (about 20nT). Actually it also makes sense, as there is no electric flow in zappicator, which can generate the magnetic field.
But interestingly, the background electric field (around 2V/m) increased to about 10V/m when the zapper is ON. Single wire attached to the zapper does not have this effect. 10V/m is quite weak, as if you just approach normal power cable of household appliance, the AC electric field goes up to 1KV/m. Do not have experience with zappicator, I am also very skeptical that it works as claimed. But there is some pulsed field coming out of it, FYI.