Plenty of savvy marketers use timers and countdowns to build buzz around upcoming products and events. If you know your JavaScript, CSS, and other web technologies, you can always build your own custom countdown timer. Plugins such as Wow Countdowns can also help. It comes with everything you need to create scarcity effect on your site.
Wow Countdowns allows you to create a countdown for a certain time or amount and track users. You are in control of various features, including title, delimiter type, increment amount, and style. The pro version of the plugin supports an unlimited number of countdowns. You can show or hide your content and use randomizers.
You can use this plugin to count up or down. Counters can be shown depending on user status. The free version of this script is available on WordPress.org.