1.) USB output to conveniently drive LED’s and other ( e.g. TTL ) devices. 2.) Very low frequncies, e.g. micro-Herz, perhaps not through the sound card but by system clock or calendar out through USB. 3.) Pulse recording through mic and/or line input with high res time stamp. 4.) Threshold for pulse recording. 5.) Level recording at fixed high res intervals.
I think Audacity will do all of those things with appropriate hardware interface. Audacity will manage sounds all the way down in frequency to battery voltage. This gets us in trouble on occasion. Audacity has a waveform drawing tool and you can make the blue waves do whatever you want.
But to get any of this work to the outside world requires a hardware interface. Some block of electronics between the USB connection and The Outside World like LEDs or other equipment.
We don’t do hardware. We’re happy to keep the software working.