Here are a couple timers using the sound of a singing bowl

EVERY TEN MINUTES: "Ding" every 10 minutes for 60 minutes. If you have this on your hard drive and playing in endless loop, you will continuously hear the "ding" every 10 minutes. Each "ding" can remind you of mantra or breath awareness of diaphragmatic breathing, or some other self-awareness practice. We leave this on here in the office of the ashram and it is a great reminder.

MEDITATION TIMER: "Ding" at the beginning signals you to begin 30 minutes in preparation for meditation (hatha yoga and pranayama). Then, after the second "ding" there is 30 minutes of silence for meditation. Finally there is a "ding" at the end of another 30 minutes (60 minutes total) that signals the end of your meditation period. Note that in the tradition of the Himalayan meditation masters, Yoga is seen as a systematic process wherein we systematically deal with all levels of our being, such that body and breath practices are an integral part of, and are intended to lead to meditation. Therefore our schedule of daily practice times is designed so that you have time for Asanas/Postures and Pranayama/Breath before and leading into meditation. We use this timer here in the ashram. A funny thing often happens after the end of meditation. Once the meditation has ended, mind feels a sense of freedom and then really starts to meditate.