Friend,

I don't think any application is designed to help prolong the battery life of a device. There are applications which help you save battery but by themselves, they don't really save battery. In short, these are just applications that automate stuff that you need to do to save battery life (such as Wifi Switcher, Brightness App, etc.).

By the way, I noticed you've been asking this question from the start as well as in other forums...you need to understand that the N900 is a Mobile Internet Device (a tablet) with phone features...it is not just a smart phone but instead it is like a mobile computer (like a netbook/notebook). With this, you need to set the expectation that the battery life of the N900 is not like the regular smart phones (which last at an average of 3-4 days with normal use).

On regular to strong usage, the N900's battery consumption will give you somewhere between 4-6 hours max and that's it. On minimal usage it can extend to probably 12 hours or so. Instead of comparing it to smart phones and thereby feel disappointed, why don't you compare it with regular laptops (notebook/netbook) or similar devices? (the N900 is a tablet anyway) Laptops using regular batteries last for only 2-4 hours or 6-8 hours using extended batteries. The N900 lasts for 4-6 (strong usage).

If you really need that much of "battery life", then the best suggestion for your situation is to either buy an extra battery or always bring a charger.