Readtime is a universal app that costs $1.99 and syncs with your Readability account. After skipping through a brief tutorial, Readtime asks you to sign in to Readability. After you sign up or log in to your account, you will see Readtime's timer. Swipe on the dial to set the amount of time you have (from 1 to 30 minutes). Tap the center button and Readtime will deliver an article from your Readability reading list. Before tapping the button, you can toggle between short articles or all articles below the timer, but no matter which option you choose, Readtime will scan your reading list to queue up articles whose length match the amount of time you tell it you have.
When you get to the bottom of an article, you'll see two buttons: share and favorites. Your sharing options are e-mail and Twitter, or you can open the article in Safari or copy the link to your clipboard. A timer icon button sits in the lower-right corner, following you as you scroll down an article -- swipe left on it to return to Readtime's timer. And at any point when you are reading an article, you can swipe left to archive the article and go to the next piece that Readtime has queued up. While you can mark article as favorites and archive them, you can't access your favorites or archives using Readtime. This is a dead-simple app for quickly accessing your Readability reading list for those idle moments throughout your day.
Readtime currently supports only Readability, but a comment by one of the app's developers on LifeHacker says support for Instapaper and Pocket is being investigated.