Platform: iOS Cost: Free
Trello is a great program if you understand how to use it. Like most things, there is a bit of a learning curve to setup and start using the Trello tracking system. I find that it works best when I use Trello in a team. When edits are made by any member of the team, you can set notification preferences for email and iOS Alerts. A great way to track larger projects that span multiple team members and to-do items.
The Video Review
Trello is a great project management application to track multiple todo and projects in a single interface. Many institutions use Trello as a system of tracking technical support issues that arise (my current workplace just implemented a Trello ticket system for tracking support requests). The software is easy to setup and distribute to a large team. Since we use it at work, it was easy for me to step into using the software for tracking my own todo list. Unfortunately, I had issues with it sending me the correct notifications on iOS. A great app, and one that cannot be beat for the price.