User cannot opt out

I was very excited when I saw this plugin as it solves a minor issue I have with my website. However there is nowhere for the user to opt out. Since I run a website for sailors who download their data via satphone, they need to be able to switch on or off their email updates. A widget would solve this problem.

For the moment, not being able to opt-out makes this plugin only half useful, which is a shame as it has a lot of potential.