The application Voip By Antisip is an easy-to-use and clever application for making sip calls. The application can be used with any SIP server, and of course with antisip.com. The only downside with the application is that it is not possible to create a SIP contact from the app. The solution for that is to use another application to create SIP contacts, and then call them using Voip By Antisip.
The app is easy to configure since it has settings predefined for a number of SIP services.
The application can be downloaded from Google play
Here are screenshots for configuration of the application with sip2sip.info using TLS: