Assume you are leaving home for holiday. It's no good getting a SMS when you are at the airport about to leave saying a battery is about to go flat! - A quick page with all the battery levels showing in one go is what I am thinkning of. Then, just chekc this page before you leave and change any battery that is low. (saves going through the sensors one by one).
Also, maybe a small bar graph on the sensor graph would be better than a line graph for a quick check?