title: Android - how do sensor readings affect battery life
body: <p>i have added a feature in my app that uses the proximity and accelerometer sensors (the second is to detect shakes). This is implemented in an always running service (if the user selects it of course). But I fear for the battery usage that my ap will have. I have NOT used any wake locks but i still get readings even when screen is off as i can see in my logs. The question is: what of the following is true?</p>
  
  <ol>
  <li>The two mentioned sensors are activated anyway by android system
  the whole time (in which case me collecting the readings as well
  does not affect battery life...i guess).</li>
  <li>Android system turns these sensors off most of the time (in which
  case me keeping them always on through my service affects battery
  life)</li>
  </ol>
  
  <p>If (2) is true: Is it possible to implement my own sleep cycle for the sensors or will the whole toggle process make things worse?</p>