I currently own a Pebble Time Steel, but I love the idea of getting an open source watch I can build my own (very simple) UI for that might outlast the hardware

I currently own a Pebble Time Steel, but I love the idea of getting an open source watch I can build my own (very simple) UI for that might outlast the hardware. I guess it's a bit like the itch of building your own desk or some beautiful wooden furniture - I like the idea of slowly refining my own watch software until it's perfectly suited for me.