You can also use a framework like Unity (C#) or Marmalade (C++) or Mono for Android instead of the NDK.
I am pretty sure that the first two have Open Source licences and google says that BlueTooth and Python integration is possible (I don’t know how hard, though)
I don’t know as much about the last one.
I might be as simple as getting a license for Marmamade, writing/finding the bluetooth integration and adding in the python library. Then again, anything sounds easy at a very high level
It might be simpler to set up the bluetooth on a PC (laptop) listening on a TCP/IP port and forwarding the commands to Hexy. That would make it simple to write the controller on the mobile device and all the bluetooth and python would be on the PC.
Good Luck,
Ralph