I just develop (my first android dev) the free app "Bluetooth Tethering Toggle" to be able to switch on/off the internet tethering bluetooth connection without to use the bluetooth settings each time. It works with the fOmey rom and others android platforms > 4.0.3, no root needed.
This application works only if tethering already works before and if the devices are paired.
Hope it will be usefull...
[Many thanks to fOmey for his great job and rom]