SensorSampleActivity nows uses SensorSampleService to do all communication with the sensors and writing to the database. If it's a sample then the Service is started, contacts the sensor, writes to the database once, and then the service is told to stop sampling. If it's streaming, then a handler is started to continuously contact and write to the database. The Service now uses a 'Wake Lock' which means the CPU stays on even if the screen is off. Can stream with screen off now.