You may already know that ‘Pure calendar’ can show Astrid tasks.
Why Astrid and not directly Google Tasks ?
Because Google doesn’t provide any API for tasks.
But Astrid is syncable to ‘Remember the milk’ service (for free).
If you sign up with Remember The Milk you can get a gadget for it that goes inside Gmail or Google Agenda. Once you do that you can link the program Astrid to sync with your Remember the Milk account.
About ‘remember the milk’ : click here
For ‘remember the milk’ google agenda gadget : click here
For ‘remember the milk’ gmail gadget : click here
An Astrid review : click here