Thank you very much for this handy module.
While playing around with it I came across this:
Important: C2DM has been officially deprecated as of June 26, 2012. At that time C2DM stopped accepting new users and quota requests. C2DM has been replaced by Google Cloud Messaging for Android (GCM). The C2DM service will continue to be maintained in the short term, but developers must use GCM for new development. We also encourage developers to move existing C2DM applications to GCM to take advantage of GCM features. See the C2DM-to-GCM Migration document for more information.
Thus I decided to add GCM support to the module.
While doing so I thought it could also be handy to have a way to unregister tokens manually by using REST - thus this I added that too.
And finally I thought it would be nice to see the Structure of the necessary REST calls and added a README.txt
The only changes left in the patch is the removal of trailing whitespaces (does my editor automatically).