I totally understand this, and apply similar tactics against my students to prevent cheating in high school science/math...
I have built limited area cell phone signal jammers - it does not damage the phones - just says no service on their phones. I have put up empty usb camera shell casings, along with fiberoptic terminal ends in random places for appearances.
This is in addition to using different coloured paper, different fonts, mixing up the questions - whether different order or multiples for values, limiting calculator usage and other things!
Why? The kids these days apparently cannot live without their mobile devices. Heck, they can't even make it through lab without looking at their cellphones to send a text to someone in the room next door! A lot (but not all) of my kids just want to know what will get them the grade.. there's not a lot of interest for the sake of learning as much at this level anymore. And their idea of what is cheating, and what isn't is vastly skewed from mine.. almost like the whole pirating/plagiarism stuff too! So I have to beat them at their own game, sadly.
Yes, I spend quite a bit of energy prepping homeworks, labs, projects and exams to make sure I have enough different versions to keep things interesting.. most of my colleagues think I am insane for doing so.. but I feel like I'm doing a disservice to the students if I don't do it to keep them focused .. and more importantly, trying as much as they can on their own for as much as they can!
For those of you that will probably comment as to - you're a *&^@#%! teacher who is probably boring.. you know what? There probably are days that I am like that, either because of content of what I have to teach because of requirements, or I am just flat out tired. But I would like to think that I try to keep it interesting by bringing things that I feel kids should see before they finish HS - like liquid nitrogen, napalm, gummi bear rocket fuel, growing silver and so on. But it's uniquely challenging to keep that level up for every class of every day! And when you have a lot of student indifference because they are there only because they are required to do so.. it's just not a great combination.