"Cuckoo Clock" is a utility app developed by Toshihiko Tambo for iPhone users. The app features a traditional cuckoo clock that chimes every hour and every 30 minutes. Users can manually trigger the cuckoo singing by pressing the switch button located at the bottom of the app. The cuckoo singing lasts for about 30 seconds. If users prefer silence, they can easily switch off the cuckoo feature.

Additionally, the app allows users to customize the alarm mode and offers the option to purchase add-ons for extra sounds, background images, and an ad-free experience. The app's URL scheme is cuckoo:// for easy access.