Is it possible to be notified before a task is due, similar to how you can set notifications for events on Google Calendar?
Google Tasks does not provide email alerts.
As mentioned by @Antoops, you can set alerts for Google Calendar events which may provide the functionality you are looking for.
It would be nice to see Google add the ability to set alerts for tasks, but I think they have left it out on purpose (since a task list is something you should check regularly by design vs. being pushed alerts/reminders)
This support thread has further reading on this feature request.
The MyTasks App for Iphone seems to access the Remind me x minutes before the due date and integrates perfectly with GTasks. Not sure where the Alert data is stored but it does work.