Found some really good documentation for the SoC used in NSA-220+ (and other). With these at hand it may be possible to figure out how to access the beeper and the other GPIO pins. The 88F5182-A2 have a 26-bit General Purpose Port I/O and maybe some unused are available, or maybe tap into the I2C bus (called TWSI in their doc). Have to read the docs and check the PCB for more than serial port header later.
http://www.embeddedarm.com/documentatio ... manual.pdf http://www.embeddedarm.com/documentatio ... manual.pdf/KC