I can also recommend Kivy, though, for smartphones, I’m still a PhoneGap fan (AppFramework seems nice as well)
Raspi+Disp is running Kivy anyhow, as I believe Python is better suited for educational purposes, easy to hack, and has nice support for Pi’s.
I was thinking of working on some HID/HUD/Accessory code for the OVMS, communicating either over Wifi (with AP or AP+Client mode), BLE, or simply streaming over an UART built on EGPIOs (the last one suffering less latency and being probably more memory tight but needs HW mods)
The “Accessory” mode would simply stream out data, and eventually accept input, all in something close to the protocol meant for Nextion’s HMI Displays
Really need to kick myself.
JB./.