Have you ever told your child "5 more minutes" (or any other length of time) and then have them ask how long that is? We can set timers and many of us usually do, but timers are not all that helpful when you are still waiting and anticipating the beeping when the time is up. I've used a visual timer with my daughter since she was about 2. She's almost 6 now and she still prefers the visual timer to the digital timer. Often these timers are sold at Autism shops or in catalogs that pertain to special education. You will find them in may preschool and kindergarten classrooms now because those teachers have discovered the timers and LOVE them. Recently I received an email with a link to an article about time timers. This article lists many different options; physical timers, iPad/phone/pod timers, and android timers. Check it out (and remember that many times an app will have a free/lite version to try it out, those are the ones I use).
20 Visual Timers for Children