The difference between a device and a weapon is the purpose to which it is put.
The little EMP "devices" have a range of about 1', and they don't have enough power to do anything more than confuse a computer (rebooting solves the problem). An effective EMP/HERF device needs about a 10' square antenna, and even then unless you have a *lot* of power behind it it won't actually do anything permanent.
Also, an effective EMP device would trash or lock up any electronics within its range - it wouldn't just set off someone's detonator, it would also lock up/jam/destroy cell phones, pagers, pacemakers, laptops and anything else that happened to pass by. This tends to make them rather obvious and annoying.
An RFI generator would not generally cause problems for passing devices - unless one of them happens to be an electrical detonator.
Also, an effective EMP device would trash or lock up any electronics within its range - it wouldn't just set off someone's detonator, it would also lock up/jam/destroy cell phones, pagers, pacemakers, laptops and anything else that happened to pass by. This tends to make them rather obvious and annoying. An RFI generator would not generally cause problems for passing devices - unless one of them happens to be an electrical detonator.