This is essentially a tens machine, re-labelled as “wearable tech”, isn’t it?
I’m in a similar position to you: have chronic back pain and try to avoid medication where possible. I did try a tens machine a few years back. (when I was in Germany where my health insurance funded it.)
I found it provided some relief, but I’d need to wear it all day, and that’s where it got unpleasant: primarily because the electrodes would move all the time, so needed constant readjustment. That I have a very hairy back didn’t help, I’m sure. Applying them to my back also wasn’t exactly easy. From a cursory glance it appears that this device might address those points.
Secondly, the constant stimulation wasn’t really pleasant either. It’s a constant feeling of electricity through your body.
I’m still thinking about trying it again, as I’m hoping the technology has evolved since (this was probably almost 20 years ago), but as others have said I’d rent one first, before buying, to see if it works for me now.