Contact pressure gauges vs. pressure switches: what’s the difference?

The field of application for contact pressure gauges, thermometers with switch contacts and mechanical pressure and temperature switches is very diverse.
Their job, basically, is to monitor limit values in pressure and temperature measurement. If a previously defined value is exceeded or is dropped below, a signal is sent which either triggers an alarm or switches off a process. But how do contact pressure gauges actually differ from pressure switches or how do thermometers with switch contacts differ from temperature switches?