Energy efficiency of Android sensors vs Bluetooth low energy sensors?

Question

I am making an android application that requires me to detect the user's motion. My application also requires me to use an external sensor, which is a Bluetooth smart sensor, for some other purposes.

Now I have two options:

1. to use the accelerometer and gyrometer of the android phone
2. fetch motion information from the bluetooth smart sensor.

I understand that Bluetooth Smart (ble) is more energy efficient than Bluetooth sensors.

However, I am confused as to which of the above options will provide me a more energy efficient solution on the Android device. EDIT: I am presently not concerned with the energy efficiency of the bluetooth device. Also, please see that I want this comparison only because I don't want to detect accurate user motion, otherwise an external device(bluetooth low energy device) would have been better hands down.

Answer 1

The accelerometer and gyrometer will take roughly the same amount of power whether it's on the phone or the external device. The difference is the external device has to transmit that information over a radio signal to the phone. It makes more sense to just use the Phone's existing information if that's sufficient because it won't require any radio transmissions and will require less power. Also, the phone will have a much larger battery.

The sensors on the phone have nothing to do with Bluetooth... they're incorporated right into the hardware.

EDIT: The difference between Bluetooth and BLE is that BLE uses the radio much more sparingly. Radio transmissions take a good chunk of power. So, using on-board sensors is going to (most likely) take far less power than using a radio to communicate with an external sensor. Also, I have a feeling that the accelerometers are always on on the cellphone so getting readings from those is going to take no more power than is already being used, too.