Paul,
Validators can only validate the data that is submitted with the form.
This means that you will need to submit the remote-addr as a hidden
form field.
Here is how you would do this:
https://gist.github.com/926824
As shown in the code above, the form defaults can be a map or a
function of the request.
In a future version, the field list may also be a function of the
request. I may also consider that for validation.
Brenton