For phones, a smart charger that connects via Bluetooth to a custom app might be a realistic workaround. The charger would just need to be able to pair and to u

For phones, a smart charger that connects via Bluetooth to a custom app might be a realistic workaround. The charger would just need to be able to pair and to understand a simple on/off command, while the app would only need to be able to pair, configure desired maximum charge, monitor the battery level and provide some form of override GUI while the phone is charging. This feature set seems quite achievable by moderately advanced hobbyists and should even be somewhat resistant to dangerous feature-creep in case someone did a kickstarter.