The iPad Mini’s form factor needs a bit of getting used to, but it doesn’t take long before your forget that it’s smaller than an iPad and that you start trying to get things done on it. In order to type quicker than with the touchscreen, you’ll want a keyboard of some kind. This folio combines a sturdy case with a diminutive keyboard, just for the iPad Mini.
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For implementing GTD you can use this application:
Gtdagenda
You can use it to manage your goals, projects and tasks, set next actions and contexts, use checklists, and a calendar.
Syncs with Evernote and Google Calendar, and also comes with mobile version, and Android and iPhone apps.