1. The app starts from BatteryAnalysisActivity 2. After clicking on the button on the UI, the activity calls the corresponding service. - For WiFi or GSM, I use AlarmManager to trigger its service periodically, once the service is called, I'd acquire a wakelock to ensure the CPU is on and ask for data from the sensor. After I get a GSM or WiFi fingerprint, I release the wakelock. - For Accelerometer, it has 2 parameters, one is the percentage of duty cycling and the other one is the sampling frequency (fastest, game, ui, or normal). The service is called every 60 seconds, once it is called, I'd acquire a wakelock. Assuming it has a duty cycle of x percentage, I'd setup a Timertask which gets triggered after (x * 0.01 * 60) seconds telling the accelerometer to stop working. - For GPS, it has 2 parameters, one determines how often we turn on the GPS sensor (sampling interval), and the other one decides how long the GPS operates once it is turned on (operation time). When the GPS is on, it asks for a GPS fix every second (it's not a parameter).