There are a lot of apps out there like MightyText, AirDroid, or DesktopSMS that allow you to send SMS messages from your PC. The problem with these services is that all the TOSs show that messages could be saved on their server. They also give pretty universal permission control to the application. While I'm sure these apps are "safe," I'm looking for a self-hosted solution, where I can host a website that my SMS/MMS content is synchronized to, and allows me to send SMS/MMS from the web browser (or companion app).
Is there something out there that does this? If not, I'm going to look into developing it myself.