Masscat has released a new version of his debugger, heres whats new:

Partial stepping - non program counter affecting instructions can be stepped. Thumb branch and pop instructions can be stepped. ARM branch instructions can be stepped.
Corrected r15 value given to GDB - GDB expects the r15 value to be the address of the current instruction not the value as if read from the register.
Avoids some data aborts when reading/writing memory via GDB - only allows access to addresses above 0x02000000.
Change to directory structure - pre-built libraries and headers are available in the libs and include directories. Debug comms source moved into subdirectories.
Some corrections.

More Info --> http://masscat.afraid.org/ninds/debug_stub.php