Profanity Filter for Rails Application

I haven't seen any but it wouldn't be that hard to RYO with word
lists. Also, you can check out which is a service
with a REST API (free for non-commercial use).

If you were to RYO, you may want to think about the following:
- converting L337-speak to letters prior to filtering (e.g. @ -> a, |
\| -> n)
- using wordlists for multiple languages