Link checker?

[Trevor Rosen]

Hi all,
I'm looking for a good automated link checker and was hoping that the Refresh list might have some opinions.  I'd want something with the following features:

Must haves:
- Runs on *nix systems
- Can be run as a cron job
- Outputs reports as HTML
- Follows 301 and 303 re-writes
- Configurable to show external links and internal links separately

Nice-to-haves:
- Email alerts
- Ability to send data output to a monitoring tool like Zenoss via REST or XML-RPC
- Written in Python or Ruby

Webcheck is what I'm using now (http://arthurdejong.org/webcheck/) it meets several of these requirements but seems to have some issues with false positives and configuration, so I'd like to look at some other options.  What have other people tried/used?

thanks for any input,

-TR