[rnhmjoj]

A quick shell version:

   while true; do if test $(factor $(date +%s) | wc -w) = 2; then echo -n '|'; else echo -n ' '; fi; sleep 1; done

[cyphar]

You can also just watch what the prime factorisation of the current time is like this:

    watch -n 1 'date +%s | factor'