It is possible in theory but there would be some research to be done unless you can find some resource out there that is doing this for you already. I am sure there are some people that have come up with libraries to access data from other languages like C or C++. In other words, possibly not an out-of-the-box solution. You do not need to focus your search limited to Processing. You could search any java module and it is very likely you can use this in Processing as it is Java after all.
You mentioned you want to get the data from the command prompt. From what I understand, you already have a program that read your NI module, correct? You can inquire this DAQ module using your command line command. As you have reported, you could use exec() to run this command and possible read the returned value returned after executing the command (This needs to be tested…). Is this enough for your case?
If the data is arriving via serial, you can try using RealTerm to see if you can capture the serial stream. If you are able to do this, then you should try the serial library in Processing and read the data stream directly. Keep in mind that if you are using an arduino, you might need to test working with two serial connections. I believe this is possible…
Kf