catcher=detector/rastreador
La idea esque la policía utiliza una herramienta que pernmite detectar conversaciones que dentro de a cárcel se suscitan entre presos o de ellos con personas en el exterior.

Appelbaum: Cell phones are tracking devices that make phone calls. It’s sad, but it’s true. Which means software solutions don’t always matter. You can have a secure set of tools on your phone, but it doesn’t change the fact that your phone tracks everywhere you go. And the police can potentially** push updates onto your phone **that backdoor it and allow it to be turned into a microphone remotely, and do other stuff like that. The police can identify everybody at a protest by bringing in a device called an** IMSI catcher**.
http://boingboing.net/2012/09/04/your-cellphone-is-a-trackin...

The BS-CATCH - Cellular Bug Catcher is a powerful tool that helps the TSCM (Technical Surveillance Counter Measure) team to detect within a period of less than 10 minutes the existence of GSM bugging devices....
https://he-il.facebook.com/bugsweep/posts/171877382893970

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Note added at 15 hrs (2015-07-21 02:53:30 GMT)
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Cada vez son más los gobiernos de todo el mundo que cuentan con sistemas que pueden rastrear en secreto la ubicación en el planeta de cualquier usuario de telefonía móvil y los fabricantes de estos sistemas se los venden.
http://actualidad.rt.com/actualidad/view/138303-industria-ra...