Re: A cheaper option in the long run?
I think the issue there is that the people doing the searching are probably the ones who supplied the confiscated items, honestly.
Personally I'd resolve that by having a set pool of search people large enough to make bribing everybody impossible, who travel around prisons randomly and get paid bonuses for finding contraband and or entry points for the contraband.
And people are using tinfoil in the direction of these devices to block them? Figure out which way the mobile base station is, and stick them that way. Fin foil it all you want, chaps. Failing that, just stick half a dozen surrounding the prison perimeter.