I just added the SIGUSR1 feature to my hacky perl script (see my other comment).
e.g.
$ (while true; do cat /usr/share/dict/words; done;) | ./randline 3 &
[2] 93937
$ kill -s SIGUSR1 93937
declinograph
brotheler
woolpack
$ kill -s SIGUSR1 93937
lustrify
brotheler
bromophenol