You could try doing it with the email cron plugin.
Create a date element that always records the current date/time (so gives you last submit time), and a simple field for "email sent" (default it to 0).
Use a copy of the list with a pre-filter that only selects rows with "email sent" of 0.
Add the email cron plugin to that copy of the list, and create a 'condition' that checks the submit date is >= 5 mins.
Add an "update" to set the "email sent" to 1.
Run the cron job once a minute. You'd probably want to do this with an actual cron job (ie. UNIX cron) that wget's a page on your site once a minute, to trigger the Fabrik cron plugin regularly (I think that's detailed in the wiki). Our cron plugin is only fires when a page loads, it's not an actual real "cron", so if nobody loads a page on your site within 5 mins ...
-- hugh