Draft for an indicator board that connects to bwack's C64Saver 2.4 (https://github.com/bwack/C64-Saver-bwack/tree/master/C64%20Saver%202)
Components have been tested in a prototype, PCB design is a draft, though. Feel free to fork and design your own.
Of course, I'm not responsible for any damages your experiments may cause to your C64Saver, your C64, or any other equipment involved.