About your power-measurement thingy:
As I noted in the other thread (not sure wether you read it), here's how I would do it:

Quote Originally Posted by jannis View Post
With ThinkPads and the "tp_smapi" kernel module you can discharge the battery even with AC connected by writing a "1" to "/sys/devices/platform/smapi/BAT0/force_discharge" (switching back to AC can be done by writing a 0 or automatically when the battery is empty). So your laptop won't power off when you got the AC adapter inserted and the discharging forced.
When the AC is connected but the discharging forced, you can read the system power usage from "cat /proc/acpi/battery/BAT0/state | grep rate".

This way you could at least automate the "charge/build new kernel/wait until battery has reached >50%/reboot - switch to battery - measure - switch to AC" cycle with accurate (and easy!) measuring.

More info (with hardware compatibility matrix) is here: http://www.thinkwiki.org/wiki/Tp_smapi
I remember you mentioning a T60 at some time so I think it would work for you.