Countdown timers are simple and you can find one for just about any device and platform. Although the concept of a timer is simple, and there are as many apps as there are kittens in spring, not all of them have a great interface. Alinof Timer is a free Mac app that is a basic timer but with an excellent interface. It has the basic alarm/alert/pay-attention-to-me features i.e., an on-screen alert that fills the whole screen and an alarm. The app lets you set a timer for up to 24hours and for as little as one minute. It can be useful if you want to remind yourself about the a meeting you need to get up for.
Launch the app and set the time in hours and minutes. Click the respective time unit and use the mouse wheel to increase or decrease the time. When you’ve got the desired time on the app, click Start. You can click Stop any time to cancel the countdown.
Click the little speaker-like button next to the time selectors to hear the alarm sound. You can hide the app using the Command+H shortcut and unhide it using the Option+Command+H shortcut. Once the timer runs out, the alarm sounds and a horizontal bar appears across the width of the screen that you must click in order to turn the alarm off.
The app is simple and only as unobtrusive as it needs to be. To dismiss the notification bar, you will have to click where it says Click to close. Randomly clicking the bar will not dismiss it.