Acceleration without gravity

I still feel I need to order second watch, just in case my one breaks down

Well if you want to that's great, but I wouldn't do it because you'll be worried you'll break it - they're made for this. Look at it this way - we've sold around 10,000 Bangle.js 2s, mostly to folks who spend a lot of time messing around with all kinds of things on them, and I don't believe I've had a single one returned that was broken by something done in software.

is there there bangle.js 3 coming with gyro?

Not any time soon I'm afraid, I'll be sticking with Bangle.js 2 for quite a while!