If you really want to open it with the default browser here is my approach:
1. Open Login Page url
2. Login then redirect to an android handled intent-filter from your app
# example: http://your-caught-login-intent-filter.example.com or
# your-app-login://scheme
3. Pass along the token and you're set
But I suggest just use the webview, then you'll have more control:
1. Create a webview, then load the login url
2. Make sure to set the webviewClient onFinishPage
3. Lookup the resulting html for your token
http://developer.android.com/reference/android/webkit/WebView.html