I recommend these all the time to the parents and teens I work with to help with time management, task initiation, homework, video game limits, chores, etc! It helps my child with ADHD stay on task and motivated with things like getting ready before school, doing homework, and knowing when his game time is up. I have one in my office as well to keep me motivated while doing paperwork.
As an adult with ADHD, I have always struggled with being on time for things and with judging and estimating how much time activity or project will take. It's called "time blindness". Once my two boys were also diagnosed, as it is highly hereditary, I decided I needed to get this both for myself and for my kids to help us better visualize time passing.
I am using this to time game times and work times in this house when I stay at home. I bought this for use as a Pomodoro Technique timer, and it has transformed my workday. I can see at a glance from across the room how much time is left. It is easy to set. This is also very handy and portable. Highly recommend it!