How to include this widget?
Unfortunately, that's not possible right now, but we will consider adding Todoist to the DashClock extension. Feel free to vote for this request: http://todoist.com/Vote_Android/showProposal/53/ and let us know what information would you like to see from Todoist on this screen?
If it's not possible right now, why have the last 3 or so updates led with "Widgets - in the lock screen too!" under the "What's New" section?
I'm sorry for the misunderstanding. Yes, we do offer a widget on Android's native lock screen. Please take a look at this short screencast to see how it works: http://screencast.com/t/auybkcDE1fk1