The timer has options for 5-, 10-, 15-, 20-, and 30-minute blocks. Just rotate it to your preferred option and the display will begin its countdown. The timer also has four different volumes so you'll never miss it going off, but you can also choose silence as an option.
Promising review: "I LOVE this timer!!! I am a school counselor with ADHD. I've tried a LOT of different timers to help me keep track of when to send passes, monitor time with students who tend to stay long to avoid class, and use the alarm to remind me to take a few minutes to eat lunch. It's fabulous to be able to just look at the time on the clock face, note that I need to leave for a meeting in 20 minutes, and bam! A quick turn of the clock and a timer goes off with enough time to grab my stuff and head out. I don't have to think about setting it like with most digital timers, and there's no annoying ticking like there is with a traditional kitchen timer. I loved my cyan one at work so much, that I bought a black one for home. It also came well packaged. Enough to protect it, but not so much as to cause me guilt as a consumer." —Laura M.
Get it from Amazon for $19.99 (available in 30- and 60-minute configurations and six colors).