Bad idea: Buy 102 of these "Energy Harvesting
Bluetooth Low Energy" EVBUM2596/D switches and build a keyboard.
They're buttons that communicate over bluetooth and don't require a battery, as they're so energy efficient that pushing the button provides the required power.
https://www.mouser.com/ProductDetail/onsemi/BLE-SWITCH001-GEVB?qs=0lSvoLzn4L8T2idaVxoXbQ%3D%3D