Complexity of emergency-only baseband development

Hi everyone, I'm building some FOSS tools that let people send/receive calls/SMS without a cell plan (mainly using VoIP carriers that also offer SMS/MMS). Eventually I would like to be able to bundle these tools with a phone that runs only free software. In order to still provide standard emergency calling features (112/999/911 calling/SMS), the phone would require a free baseband (like OsmocomBB), but it would not need to offer any non-emergency phone features, since those would be handled by the aforementioned FOSS tools primarily on wifi. As I understand it, OsmocomBB can currently be run on certain Calypso-based phones, but does require a larger computer be connected to run part of the baseband. If one were to only require emergency calling features in OsmocomBB, would that larger computer still be required? If so, would developing the remaining pieces needed to run directly on the phone be substantially easier for an emergency-only use case than for a complete all-purpose use case? I'm guessing that there are certain parts of OsmocomBB that would not be required for emergency-only operation (perhaps some of the SIM card communication, for example), but I haven't written baseband software before so I don't have a good sense of how large the differences would be. So I'd be curious to know if the emergency-only use case is substantially easier to develop for, or if it's roughly the same complexity as developing for the all-purpose use case, or somewhere in between. My apologies if this isn't the right list for such questions; I'm happy to post elsewhere if that is more appropriate. Thanks for reading! Denver http://soprani.ca/