A script called Tani Lipi was developed a few years ago by Tony Koyu for writing the Tani languages of Arunachal Pradesh:
Tani Lipi received support from the governor of Arunachal Pradesh in August 2010 (press release) and was endorsed by the Arunachal Tribal Union (AIPU) in January 2011.
However, there is some skepticism about the practicality of adopting a new script instead of using existing writing systems. Some concern has also been voiced about the intention of promoting Tani Lipi as an official script of Arunachal Pradesh or as a common script for all languages of the state.
I prepared a brief document that introduced Tani Lipi to the Unicode Technical Committee. A new proposal is currently being developed. Any information about the script is welcome.