i want to make a prototype of a watch for waking up me in the night in order to take care of my daughter.

this watch includes arm based MCU with time display on panel(OLED or LED), vibrate, beeper. using 3D printer for the box of this watch.

considering i might make other toy base on the same platform in future, it is important to choose an extensible rtos. i choose the rt-thread in this watch. here is the link. rt-thread is a open source real-time os, includes the rt-thread kernel, FinSH shell(C expression shell like Vxworks), filesystem, Lwip, GUI. and support widely architectures. including lots of arm cortex-m0, cortex-m3, cortex-m4 MCU.