Slack Apple Watch App
Slack isn't an a To Do list, but it is an essential productivity tool for many teams. The Slack Apple Watch app lets you communicate with team members, using canned replies or voice dictation. It is easy to see messages that you would normally get a notification for and you can also switch teams right from your watch.
You'll still need to use the Slack app on your iPhone and computer, but now you can quickly stay in touch when you don't want to grab your phone or go back to your computer. Slack is free on the iTunes App Store.