We have recently written about two FREE applications one of them is a free low battery laptop alarm and the other one is Battery Bar which shows you the remaining time and power left in your laptop battery before it drains out completely.
PowerMeter (via LifeRocks 2.0)is another free tool which displays the amount of battery power left in your laptop battery, one of the amazing feature of this utility is the horizontal battery bar becomes more visible and the colour changes as the power level of your laptop battery becomes more critical.
When the battery is nearly full ( above 80% = green, below 20% = red, in between 80-20% = orange)
Half empty, more visible and more alerting color
You can further configure PowerMeter further to change the behaviour to check the power meter settings.
You can set to hide the horizontal battery bar when battery is full, and check the option Warn me when the power drops below 20%