A free app for Android, by Voizarabia Limited.

PKCall is a free application that can be used on your Android device to make VoIP calls to any other phone, even if it is not connected to the Internet. You can choose between three methods of calling: the standard SIP method, the H.323 protocol, and the SIP method with a Phonebook. You can also choose the network to which you want to connect, the type of connection, and the port.

The app has been developed for the requirements of VoIP providers. The main objective of the app is to provide a good user experience and to be compatible with various standards.