Hi Ricardo, At the moment we are not notified when a customer leaves a review. Just like when a sale is made we are not notified through email until you log into your Merch account and lick on the 'Analyze' tab. Hope this helps.
Ricardo, you could try the following, although I'm not sure how well it would work for an update like this. You can set up a browser alert, the addon for Firefox is called "Distill Web Monitor", input the URL of your t-shirt and if the page changes (like a review is added) it will alert you. There is a similar one for Chrome I think.