The problem with cell phone blockers used in some eateries and theaters is summed up by a Motor Cycle instructor who told his students something like:
"Unless you are something like a transplant doctor subject to 24 hour on call TURN OFF YOUR PHONES and poagers because I do not want you distracted when it rings"
A hand went up... Uh, sir, I'm a transplant doctor.
Imagine you or your loved one is in hospital, All preped and ready for that new body part, the decaseed with the new part has been "Harvested" and it's waiting for installation.. and the doctor can not be reached because of a cell phone blocker.
Now you know why that device is illegal, plus of course it is interfering with a federally licensed radio transmission. (Big no-no)
For the gent who mentioned the bit about AX.25.. Know it well
Yes, it is possible to have many different routers on the same channel, but why run the risk of data collisions (Which show up as reduced bandwidth by the way, they are NOT reduced bandwidth but that is what they look like, Slower speeds) if you don't have to?