[petra]

What do you mean by flexible ?

As for the wristband, have a look at hexiwear, and the hexiwear battery pack(which may be wearable). it has BLE and it does support "Firmware Over the Air update", i think.

[daviddumon]

In my mind, it was something like that :

https://news.panasonic.com/global/press/data/2016/09/en16092...

Flexible batteries you can embad in a tissue wristband for example. But I don't know if it's possible to do so.

Thanks for the link I will check it out asap.