As a current prisoner, I'm not sure this guy had it right. It's usually the guards that supply cellphones and they just bring them in pockets or bags. Or nuns. I had a nun smuggle in a C# book with accompanying CD-ROM.
Drugs often travel in your "prison pocket", but I've never heard of anyone jamming a cellphone up there.
Luckily, before I went to jail, I had been given this book, the knowledge of which proved useful inside:
There are usually dozens of places to hide things that don't involve your anus.
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