With that great Battery eye app showing the decline of the battery is it not possible to create a desktop widget that will calculate the battery expiration time?

Could someone develop an app that will give a time of when the battery is likely to expire based on the current usage. Basically, whatever you are currently running at the time the battery expire widget would show you a time when it will reach 0%. Or be able to configure it to warn or alert you when it reaches 5%.

This could be useful for estimating if you need to take a charger or extra battery with you when going out. It would also be useful for ensuring that you can have enough battery power all day by warning you that a running a current app or browsing the net will mean that your N900 will run out of juice before you can get home.

Any takers?