Quick question: is there a way to access the review queues on the mobile site or StackExchange app?
I don't see anything, but it seems weird to not be able to review content on the move.
As commented by several of us the way to do this on an iPhone is to first access a browser by using the button at the lower right to access this menu where I choose Open in Chrome (you may instead see Open in Safari).
Once that option is chosen you can see the review count on the screen below which can be clicked to open the review queue.
Personally, I prefer to perform reviews when I am back on a laptop but I use the above when the action to take seems simple.
If you decide to search/ask for this to be implemented in a mobile app at Meta Stack Exchange then be sure to specify whether it is iOS or Android that you are wanting because the two development cycles are far from in sync.