That's cool, the soundcard in a pc can probably generate signals down to 10hz too.
But your idea of an external signal generater has got me thinking, It actually might be worth the effort to build a dynamic test device that could run different profiles and have the guino spit out the lcd data out the serial port, and have the test device confirm that the serial data looks right (aka regression test).
Here is what an acceleration profile might look like, roughly:
, so the testing device would run this through the guino, and see if the current/tank trips looks right when it is done. Also the static inj and vss pulses would be checked on the instant data at various spots. But it would be easiest to implement it with another duino.