If you are curious about your N900's battery and want to check it how its draining then this app is for you. Battery eye provides graph for battery percentage, chrage and volt. It's a must have app for every N900 owner.
As the Author of the App says in Battery-eye description:
''battery-eye is a small app, that records battery data (percentage, current, voltage, charger status) continuously in background, and creates a graph to visualize how the values change over time. It also calculates statistics on average battery usage, and battery life estimates based on that.
The data collection process is designed for minimal impact on system performance and battery life.''