Was procontrol Google, but never managed to find a way to determine the charge level of the wireless Logitech devices under Linux. To Win the battery level can be seen with the program Set Point.
May be somebody met the decision under Linux?
PS With a mouse is more or less clear — a visual charge level is displayed on the device itself (I have a Logitech MX Revolution). But with the keyboard (Logitech DiNovo Edge) is more complicated. Until the level drops to 15% to define it will fail. Unless, of enable/disable keyboard.