Tumblr allows you to search tabs and then mark to track them. Once you have these tags tracked you'll see how many (up to 10+) posts related to that tag have been updated since you last looked at that page.
The problem is that these tracked tags aren't made available anywhere but on the Tumblr dashboard. Tumblr's mobile site and mobile app don't include these things as a menu option.
Does anyone know of an app or service that allows you to tie in with your Tumblr tracked tags?