You'd be even more impressed if you saw just how little resources they have to use (ram, storage, cpu), or how old of a C standard they have to work with. I have a few friends that work on this.
And also — sadly — Monkey C. I cannot imagine what possessed them to invent their own scripting language for wearable device apps. It's sort of like JavaScript but worse and with minimal third-party tooling support.
it kinda sucks, but with the constraints it's at least understandable. they wanted an extremely lightweight language with a bytecode VM which could be ported to whatever MCUs in 2015, while also strictly limiting the functionality for battery usage reasons (and, uh, product segmentation/limiting third party access).