No, I don't think there is an App that would accomplish what you're trying to do. I mean, there are Apps out there to set different LED colors according to each alert, but not for when the device is charging. So unfortunately the LED will only flash while the device is off and charging.
__________________ Tony "Some things Man was never meant to know. For everything else, there's Google."
"I'm not anti-social; I'm just not user friendly"