What common applications of electronic monitoring or surveillance equipment are there?

Paul Brookes has written:

'Electronic surveillance devices' -- subject(s): Electronic surveillance

is when all the persons that are under surveillance know that they are being monitored or recorded...

Robert S Mueller has written:

'Electronic surveillance manual' -- subject(s): Handbooks, manuals, Electronic surveillance, Eavesdropping, Wiretapping

Electronic audio and video devices are never used by terrorists for surveillance purposes.