Getting _information_ about power usage is (theoretically) fairly easy. You need to know the current voltage of the battery, and the amount of power that's being used at a particular moment. You then average the power usage out over the last few minutes, normally.

You know that at a particular voltage, the thing will shut off. You also know that, when you're using a certain about of power, it will take a certain time to reach that voltage.

The _hard_ parts of power management are making drivers for hardware that can go away and come back cleanly - and that has been done very well on the 770. It generally has some of the best power management of any PDA out there.

I don't know if the 770 has good power measurement hardware. I suspect that it probably does. However, I don't think that Nokia currently lets developers get access to _any_ battery state information. Thus, what you want will be relatively easy to implement once Nokia opens up an API to read the info.

Until then, sorry, not much that developers can do.