The "Casio G-Shock Smart Sync" app is the only Non-Casio app out there, which works with the actual G-Shocks and which is actively maintained, meaning it gets regular updates.

The app is developed by Ivo Zivkov and is available from Google Playstore, F-Droid or GitHub.

One big benefit of this app is, that it does not require to create a Casio ID.

Connecting a watch with the app is super straight forward. Open the app and than trigger app connection on the watch.

Casio G-Shock Smart Sync offers a lot of features, e.g.:

• Sets watch's reminders from Google Calendar
• Automatically sets correct timezone when travelling.
• Trigger actions on the phone by pushing a button of the watch like taking pictures, dialling a phone number, etc.
• Configure most watch settings from phone.
• Sync phone alarms with watch alarms.
• Automatic time syncronisation (only last paired watch, not multiple watches)