'Phonebloks' pitch video describes LEGO-like modular gadget idea

I should also remind folks, I suppose, that external battery packs are already available. Modified “bump guard” cases that carried a second battery were one of the earlier accessories sold for the iPhone.

Yes, batteries wear out. Yes, that means devices with batteries sealed inside them will need Really Annoying maintenance eventually. That’s the engineering tradeoff – if you can’t live with that, buy a device which makes swapping the batteries less painful.