How about using your cellphone for that?
I sometimes use my Sony Ericsson K750i for it (just for taking reminders-to-self) and have created a joystick shortcut for "record".
Your phone may vary, and sensitivity may be an issue (external microphone possible?), but it does the job for me. Recording capacity may be a problem, too, if it doesn't use a memory card for that.
Accessing the recordings and even seeing there are any recordings on the machine to remember sucks, however, on my phone.