Todoist is a task manager radically minimalist but effective works on many substrates. In fact, the service launched five years ago now has its own mobile applications for iOS and Android, in addition to already available on the Web, Mac, Chrome, Firefox, Outlook and Thunderbird.
This free service allows you to manage an unlimited number of tasks and organize them into projects, while accessing the task manager while offline and saving everything in the cloud to provide synchronization between all devices day. The paid version offers including notes on tasks, system tags, access to iCalendar tasks, synchronization and permanent reminders via SMS or email notifications to the mobile ...
Web applications like mobile task manager offers login or register early with your Google Account. IOS and Android applications are a bit like the service: simple and functional, with good use native components of mobile OS.
While there are many free task managers, it has the merit of being clean and complete, and to be accessible everywhere. There are also Any.DO in the same genre quite minimalist.