GoTasks is a 
Google Tasks client for iPhone and iPad.
Features:
- Works with Google and Google Apps accounts
- Multiple account support
- Search functionality
- Inplace tasks editing
- Notifications of upcoming tasks
- Various sorting modes (by date, by title, by status)
- Badges showing the number of tasks (due, overdue, today)
- Highlighting overdue tasks in the list
- Offline mode (create/edit tasks offline and sync later)
- Data is sent securely over HTTPS to Google
Google Tasks client for iPhone and iPad.Features:
- Works with Google and Google Apps accounts
- Multiple account support
- Search functionality
- Inplace tasks editing
- Notifications of upcoming tasks
- Various sorting modes (by date, by title, by status)
- Badges showing the number of tasks (due, overdue, today)
- Highlighting overdue tasks in the list
- Offline mode (create/edit tasks offline and sync later)
- Data is sent securely over HTTPS to Google
Links and Download
Recent user activities on GoTasks
- braky added GoTasks as alternative(s) to Nextcloud Tasks
This is something I was looking for, it manages and synchronise tasks with Gmail/Google account, so that the online task and task on your iPhone/iPad are in sync. It can manage multiple Gmail/Google accounts and holds the data locally, so if you do not have access to internet you have the local copy to work on and synchronize it when you have connection. You can assign different colours to your multiple accounts. I love it.