Switching power to a sensor
Probably- one method would be to use a P-channel MOSFET as a high-side switch to control the 'sensor' power. You might have to add a pull-down or otherwise ensure that the output of the 'sensor' was close to 0V with no power- if it is allowed to float around the MCU power consumption might increase. 

There are many inexpensive logic-level MOSFETs that will work fine from -3.3V gate voltage with guaranteed very low Rds(on) and reasonable guaranteed leakage. 







simulate this circuit &ndash; Schematic created using CircuitLab

You may have to ensure that the 'sensor' supply has some series impedance or that the MOSFET does not switch too rapidly if the 'sensor' has large bypass capacitance- otherwise it could glitch the MCU power when it turns on and cause problems.