Power / battery / sleep

Just a follow-up question on deep sleep - if 3.3v pin and GPIO pins stay on during deep sleep, presumably I am better powering sensors from a controllable GPIO pin so as to minimise draw during deep sleep, something like the code below.

For larger stuff that needs more current than a controllable pin can supply, presumably I need a transistor connected to 3.3V, the controllable pin and common ground in order to switch them off during deep sleep?

// button will be wired from 3.3V pin to A8.
// other sensors will be wired with +ve to power pin B1 and their own ADC pin to read
var powerPin = B1, btnPin = A8;
var watch;

function doStuffAndSleep () {
  setDeepSleep(0);
  //power up sensors 
  digitalWrite(powerPin,1);
  //check sensors...
  //...check completed
 //shutdown power and go to sleep
  digitalWrite(powerPin,0);
  setupWatch();
  setDeepSleep(1);
}
function setupWatch () {
  setWatch(doStuffFromSleep, btnPin, { repeat:false });
}

doStuff();