Now when the ClientLogin authentication is deprecated should we use OAuth 2.0 for C2DM messaging?
My application is C# web app that needs to send messages to registered devices. Any example how to get an Auth Token with OAuth to use with C2dm messaging? Which type of authentication I need to use (Installed Applications, Web Server...)?
Edited 28 Jun, 2012
C2DM is deprecated. Developers are encouraged to switch to GCM, C2DM will be supported for a short time. Simple API instead of ClientLogin and oAuth2 which are not supported. http://developer.android.com/guide/google/gcm/index.html
Android C2DM still requires that you use Client Login authorization. oAuth 2.0 is not available for C2DM yet so implement Client Login. As Warpzit says Google's deprecation policy states that it does not apply to experimental features, and cloud to device messaging is still considered to be in the "labs" state.