We analyse and evaluate the sensitivity and robustness of an eccentric fiber Bragg grating sensor micro-structured into a polymer optical fiber under different relative humidity, temperature, strain and torsion conditions. Relative humidity and temperature conditions are established with a climate test chamber and prepared salt solutions. Though made of polymer, the cross-sensitivity of the sensor to relative humidity is low, enabling usage in rapidly changing environment applications, e.g., for movement detecting gloves or in vehicles, but also in high moisture situations. We find a linear dependence on temperature, so that either bending or temperature can be measured separately from each other. After rotation of one end, the sensor measures torsion by observing the light intensity and the change of the full width at half maximum. Strain measurement shows multiple elastic strain regions before final plastic deformations occur. In the next step, the flexible sensor system will be implemented in a sensor glove to monitor finger movement and detect different hand gestures.