SFOS still missing features that almost all devices has support for today such as bluetooth profiles(RFCOM?), usb host mode etc... and QT API to use internal/external sensors, bluetooth etc.
It is a really shame every time I see a youtube clip where they use some Android device to connect to a sensor or STM32 Nucleo, Arduino etc... I often think: "Hey that I should do with my Jolla Phone" then I realise: "I need that X API, lets see if Qt has this. I should forget this I need Qt 5.4 making that work " or "I need USB Hostmode"