I'm not sure beta voltaics will ever reach LiPo densities. All materials I know would be unwise to place in your wallet, or anywhere near your body.
If we are OK with a battery and a beta voltaic source, a tritium one is reasonably safe and can trickle charge the battery when the device is in deep low power mode. The battery can still be charged by the induction coil.
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I would love if the screen could take up more space, even at the expense of a little extra thickness.
I think that there could be a wider screen if such formats are available. Once we have betavoltaic batteries, the entire card can be screen.
I'm not sure beta voltaics will ever reach LiPo densities. All materials I know would be unwise to place in your wallet, or anywhere near your body.
If we are OK with a battery and a beta voltaic source, a tritium one is reasonably safe and can trickle charge the battery when the device is in deep low power mode. The battery can still be charged by the induction coil.
That actually exists, with even the same CPU but no NFC: https://www.xteink.com/products/xteink-x4
That looks like it's the size of a smartphone. It's 7 times thicker... I'm not sure that qualifies as a little thicker, plus all the other dimensions.