sierramike

This widget allows you to display a JQuery responsive countdown timer on your website. You can use it as a widget or include it wherever shortcodes are supported.
It comes out of the box with french and german translations.
The widget contains media queries in its css stylesheet. You can edit it to suit your needs.
This widget also supports shortcodes!
Just add a [smcountdown timerdate=’xxx’] shortcode to any of you posts and you’ll get a responsive countdown timer! 
The shortcode supports one parameter: timerdate. 
* timerdate indicates the target date until which the timer counts down
Shortcode usage samples : 
[smcountdown timerdate=’2015/12/31 23:59:59′] 
Displays a countdown timer until Decembre 31th of 2015, 23h59m59s.

SM CountDown Widget

Displays a responsive JQuery countdown timer.

Kanopi Studios

This plugin is no longer actively maintained or supported. 
You may continue to use it, but please be aware that it may not be compatible with future versions of WordPress. We recommend considering alternative solutions.
When launching your site there are usually a series of things you do before you “go live” to validate your site is ready to go. This plugin provides an interface for managing that checklist through the WordPress UI.
The plugin integrates with <a href="https://github.com/a11yproject/a11yproject.com" rel="nofollow ugc">The A11Y Project</a> and will pull a list of current accessibility tests to check against. The way to add those extra items is through the settings page for the plugin. This feature uses the <a href="https://www.jsdelivr.com/" rel="nofollow ugc">jsdelivr</a> service for fetching the data. You must agree to the <a href="https://www.jsdelivr.com/terms" rel="nofollow ugc">jsdelivr terms</a> to use that feature.

Launch Checklist

WordPress plugin that allows for creation of interactive site launch checklist items.

SM CountDown Widget vs Launch Checklist