Retrievable sensor devices and methods are provided that can be easily installed and removed from a sub-sea system without the need to stop the flow of working/process fluid. In particular, a retrievable sensor is provided that can be configured to be located remote from the process fluid to allow for easy access. In other embodiments, an actuator is provided that allows for pressure adjustments to be made during installation and/or removal of the sensor so as to avoid damage to the sensor and/or other system components and to avoid any process fluid/material leakage. Methods are also provided for installing/removing a retrievable sensor, as well as for adjusting a pressure of a retrievable sensor.