This battery monitor talks to the host (Teensy in this case) via I2C although battery status is available via an interrupt also. In both cases, host intervention is "required" unlike the basically passive existing
charger.
But more importantly, the part is ~$2 which means I would have to charge $15 for a charger with the monitor as opposed to $10 for the current one. Is it worth 50% more for a gas gauge? I have been thinking of redesigning the LiPo battery charger and I have a target chip in mind that does allow a battery fuel gauge capability, also with multiple alerts. The alerts would likely be different colored leds, maybe from a small rgb led, and maybe a host interrupt but this isn't really necessary. The decision is who is responsible for checking an alarm, the user or the host?
Also, I'd like to keep the cost low.