This is one of my long term goals as well. After I (hopefully) figure out how to get either the TI compat-wireless stuff to work and/or latest backports for hostAP mode to work, BT4 LE would be next. I have no experience backporting, but going to try. I have gotten much farther in getting TI-compat to compile. It seems to clash with some patches in the stock kernel. There are also things from kernels 2.6.37 and back that are needed. The official patches cannot just be simply applied due to Nokia's changes. I have a spreadsheet and what I believe are the relevant patch files I'm working from. Hopefully I learn something and can move onto BT4. I assume IRC will be helpful there from the bluez group. Meantime, any links to the aforementioned work by others would be immensely useful. Research is easily done in spare time.