You can probably get rid of the USB layer because you don't need to access the port as long as the battery is charged.

Yes, unfortunately hardware, it will probably just be a simple resistor voltage divider. There isn't a good software workaround unless you can tell the software when it has a full charge.

Keep in mind that the current hardware with the <3.3V low battery warning, which means maybe 5% capacity, can last a while in standby mode, depending on what else you have connected.

Excuse me for asking if this isn't appropriate. About how long till the new hardware revision? I want to build a smart watch soon but depending on the time frame would be willing to wait if it means I get to know the battery charge level.
Thanks for your help!