Any physical device can be subject to physical abuse. These things aren't made out of titanium. I think they're largely made out of reinforced plastic. There's waterproofing; there's the whole issue of whether you can tamper with them, whether you can use electronic devices to interfere with the radio signals. All of those things are possible to some degree. It's a question of to what degree you want to make these things tamper-proof or make them hard enough, if you will, that they don't interfere with the individual and yet can't be cut off.
These are all trade-offs in the design of the device. You need to say that you need the device to be able to do this, and it can't be cut off with this type of instrument. It needs to be able to withstand an electric field from at least two feet away.
These are the sorts of technical specifications we talk about.