Sukima
Study your Anki reviews on your Apple Watch, in the gaps of your day.
Sukima sends your due review cards from Anki on your Mac to your Apple Watch. Answer them with a swipe. Your answers are saved back into Anki, and Anki schedules every card as if you had studied it there.
Sukima is an unofficial companion for Anki. It is not made by the Anki project.
You need: a Mac with Anki, an Apple Watch, and iCloud. Sukima has three parts: the free Sukima for Anki add-on, Sukima on your Mac, and Sukima on your watch.