Listen fifo and socket files
I have two process, which speak with fifo or socket file. Can I somehow read the information they are exchanging? If some of information crashes, I don't care.
Somehow? Of course, somehow. Write a kernel device driver. Or, for a really big challenge, open /dev/mem and figure out where the information happens to be :-)
You'll need to be more specific in terms to get a more useful answer. Do you have root access? Are you willing to leave traces? Are you willing to attach ptrace/strace to one of them?