The peak strength of the magnetic field of WTMDs is at most a few gauss (a gauss is a measure of magnetic flux density, commonly referred to as magnetic field strength ) at the surface of the field generator. The magnetic field strength then rapidly decreases towards the center of the walk-through gate. The earth's magnetic field, for comparison is just a bit less, at roughly half a gauss. The reason the WTMD is so sensitive is because the magnetic field varies rapidly in time, and interacts with any metal in proximity which changes the time-varying characteristics of the weak magnetic field. As a further comparison, it would take several thousand gauss or more in immediate proximity to a magnetic disk drive to erase the data.

So, I wouldn't worry too much about a WTMD affecting any electronics all that much!