A couple of months ago, Google launched Tasks in the Google Mail Lab. Unfortunately, you couldn’t take those tasks with you and check them from your mobile phone. Well, now it’s possible and Google also added something special for iPhone and Android users. Those users get the ability to add, edit and delete items from within the mobile device.

All you need is mentioned in a requirements list.

You have to do is enable Tasks  in Google Mail Labs. If you do, you can view tasks, add new tasks, and also check them off as all taken care of. Any changes to Tasks you make via your mobile phone are reflected in your Google Mail account.

You can watch a little Tutorial for the iPhone from googles youtube channel.