I have the 404 email mod installed which sends me an email on a 404 Page Not Found Error.
It uses a simple observer firing on NOTIFY_HEADER_END_PAGE_NOT_FOUND.

I have an odd problem...I get a set of four emails triggered by a view of one particular product page.
The queries as reported by the email are:
[/tienda/undefined] x 2
[/tienda/2012%20V-Strom%2018%20Adventure%20Light%20Gray_files/].
[/tienda/Vstrom_2012_files]

These queries are indeed invalid and the latter two are related to image links in the chunk of flash-images embedded in that page.
The page displays ok, validates and no site map or 404 error is ever shown.

These emails/errors only occur when CEON URI mapping is enabled.

So I am unsure if the "issue" is with the 404email or there is some black magic URI re-handling of the 404 going on.