Is it possible to wake up an Arduino board using the output from an accelerometer such as ADXL345. Say if the output value if larger than a number wake up the board. Is it possible for both analogue or digital pins to do this?
You use the two interrupt pins only. These can trigger in an event, like exceeding a value, tap, double tap and free fall. See page 20 of the data sheet for details of how to do this.