Timeful was a TODO/task company, they just approached the problem in a different way, by arguing that the calendar and the TODO list should be the same app, not separate apps.

The idea was to have a TODO list with actual time committments associated, and you had the ability to actually schedule your TODO by slotting them into your calendar.

Functionally, it was a great idea, but it suffered greatly from a lack of integration with most other tools on the market. If Google runs with it, it could be interesting, hopefully they actually do something with the idea.