Hey guys;

While messing around with some .mobileconfig files (the files that are being created by the iPhone configuration utility) I stumbled over some undocumented features (like setting a few chosen defaults inside the iPhone OS to enable verbose logging features)

My goal was to enable the numerical battery status applet WITHOUT jailbreaking the phone. I failed. It's not possible to change the corresponding default in com.apple.springboard using a .mobileconfig file. (SBShowBatteryLevel is not listed as a manageable default in AllowedDefaults.plist)
Nonetheless...
I found an option called PowerLog.

When enabling this (and after a restart of the SpringBoard) the iPhone starts syncing a PowerLog logfile to iTunes everytime you connect the device.
This file contains some pretty valuable information about all background tasks (and foreground too of course) and their power consumption.

I wrote a quick How-To and posted it to the MR-forums... take a look at the post here: Battery Problems with 3.0? Try the "Battery Logging" Setting to gather Logs - Mac Forums

If you don't need no stinkin' how-to you may download the .mobileconfig file here: http://bit.ly/powerlog (point your iphone's browser to this url to install the config profile immediately - otherwise use your mac/pc to get the file and peek inside if you don't trust me - and then mail the file to your device to get it installed)