- None of the radio specific apps will work without having the service installed as they use the service for SIP calling and VOIP audio
- The service must be installed no matter which radio specific app is used. It handles the SIP and VOIP audio between the RRC and the installed App.
- The service will only install on a phone which supports both SIP and VOIP
So there is no meaning to install the radio specific app if you can't install the service as its the service who do most of the work. The radio specific apps do not use SIP or VOIP them self as the just communicate with the service, which then does the actual communication work (SIP & VOIP).
When I say that you device apparently doesn't support SIP or VOIP, I mean your phone and not the RRC device. There are some models and brands that has SIP and VOIP disabled. If the service isn't listed in Google Play that means that your phone does not support SIP or VOIP. The radio specific apps will be listed as they don't need SIP or VOIP, only the service does.
I will try to find out how to make this more clear on our website. Maybe the best thing would be to force the radio specific apps to be dependent of SIP and VOIP also (although they actually are not). That way they would not be listed either for a phone without the SIP and VOIP support.