I also wrote a filter over Twitter for iambic pentameter once, and had a friend write a web frontend to it. Here's my (messy) code; http://glozer.net/ wrote the frontend in Erlang but AFAIK never released it.

https://github.com/darius/versecop

Pentametron is cooler. I did try filtering for rhymes too, but there wasn't enough data in the free feed, at least back then.