Please tell me what that utility is--I've long wanted something like that but have yet to find anything like it.
FWIW, I've been doing something similar with my phone, but manually. I found an unusually low current charger that charges the phone at a rate of ~5% per hour, and I almost always keep the battery level between 25% and 75%. So far the phone is 4 years old and iOS claims that the maximum capacity of the battery is still 92%.
