I want to obtain a Google Authtoken from the AccountManager that I can send to my Webservice (not hosted on App Engine) to authenticate the User (I just need the email address and eventually his name, if no permission is required for this).
What do I have to use for the "authTokenType" Paramter of the "getAuthToken" method?
And which google Api do I have to use to get the Users Email?
This is doable using OpenID Connect, however it's sort of experimental, so details could change in the future. If you get an OAuth token for the 'https://www.googleapis.com/auth/userinfo.email' or 'https://www.googleapis.com/auth/userinfo.profile' scope you can use it to get user info from https://www.googleapis.com/oauth2/v1/userinfo (including email). Of course the user needs to authorize this.
You should theoretically be able to get the token from AcccountManager using the "oauth2:https://www.googleapis.com/auth/userinfo.profile" as the token type, but that doesn't appear to work on my device (Galaxy Nexus with stock 4.0.4). Since getting a token via the AccountManager doesn't work (at least for now), the only reliable way is to use a WebView and get one via the browser as described here: https://developers.google.com/accounts/docs/MobileApps
There is a demo web app here that does this: https://oauthssodemo.appspot.com
(late) Update: Google Play Services has been released and it is the preferred way to get an OAuth token. It should be available on all devices with Android 2.2 and later. Getting a profile token does work with it, in fact they use it in the demo app