Firmly pressing using Force Touch brings up an option to add tasks using the Apple Watch's built-in Voice Command dictation, and tasks can be categorized into the main Inbox, assigned to a project or given a timestamp of today, tomorrow or no date. Filters and labels provide additional layers of categorization for your to-do lists, with the latter requiring Todoist Premium for $33 per year.
Todoist for Apple Watch also features notifications for new comments on shared tasks, when you are invited to a new project, when you are near a certain location or at the exact date and time when a task is due. Tapping on a notification will bring you to the full app, where you can view or edit the task at hand.
Todoist for Apple Watch will be free on the App Store and should be rolling out today pending approval.
Update 8:53 AM: The 10.1 update with Apple Watch support is now live in the App Store. [Direct Link]