It does NOT allow you to call from your Android phone, the call is just automatically initiated for you.
If you have an Android tablet at home and want to call someone with your sipgate phone just click on a contact and the app will connect you (similar to click2dial)
You can also send SMS via sipgate.
This app does currently not work with the default contacts app or the default dialer in Android 4.3 and 4.4 due to a bug in android, see
for more information.