In the process of converting an AC signal to DC, some USB wall adapters will leave a lot of noise, sometimes with an amplitude of up to half a volt (for 5V chargers) [1, 2]. This can damage devices and permanently decrease battery life. I’m thinking about designing a replacement charging cable that would test the signal and if it was harmful, would light up red, warning you to discontinue use of the charger. Otherwise it would function as a regular microUSB/USB-C/Lightning cable. What do you think about this? Is it something you/others would use?[1] http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html
[2] http://www.lygte-info.dk/info/usbPowerSupplyTest%20UK.html