I would like to implement a feature that only delivers messages to devices at specific periods. After the valid time, messages would be abandoned. Can anyone suggest me how to do this?
Google just released a new version of c2dm called "Google Cloud Messaging (GCM)" at I/O 2012. With GCM its possible to define a timeout for your messages.
GCM ttl section: http://developer.android.com/guide/google/gcm/adv.html#ttl
You can find my answer to a similiar question here: https://stackoverflow.com/a/9709944/789738