For what it's worth, I'm re-writing the Robo app (currently only iOS) in PhoneGap with Framework7. I've been playing with the OctoPrint API and am now comfortable with that. So I'm just researching the existing app by Robo3D and then coding it in HTML/JS/CSS. I considered adding React to the mix but I dunno, maybe if I feel like it later. Hard to say if it's worth the trouble until I get further into it.