Hi,
No - you have no way of controlling the red LED in the Beo5. It is controlled by the application itself. Since it is placed on the back part it makes only little sense to let it flash indicating a low battery level. Using the white backlight (which you cannot control either) will draw a lot of current which can cause a voltage drop restarting the Beo5 which makes it a bad choice.
Therefore - when using the remote, it will display that it needs recharging. If you are not using it, it will turn off at 20% (if I remember correctly) battery level allowing you to turn it back on and use it before it really needs a recharge. At a lower battery level it will turn off shortly after you turn it on to make sure you recharge it while making sure that the battery is not completely drained.
Also, you cannot control the internal speaker to give an audible warning. The speaker is used for the wheel click sound only.