[16s]

Collect cellphones at door. Put them in steel cabinet. When workers leave, they can get the phones on the way out.

[Jach]

But they'll never expect you to have two cellphones!

[nwombosi]

How about one of the microfilm devices they used to use in 60s spy movies?

[lelf]

You mean Google Glass?

[tomjen3]

Because no person has two cellphones.

[16s]

If you are willing to risk smuggling one in and are foolish enough to think they cannot detect the radio waves, then go for it.