Vintage Synth Repair

With the advent of virtual synths allowing our computers to act as 
real synths, I got to wondering something.  Has anyone developed a 
program that would allow a computer to act as various pieces of test 
equipment?  Rather than having to go out and buy a separate o-scope, a 
multimeter, etc., why not have all those functions available on your 
computer screen?  It would require a special card in your PC of 
course, but wouldn't it make sense?

Just wondered if such an idea was already out there.

Rob