The current battery state of the K-x is recorded in the EXIF data stored in images taken by the camera.
This may or may not be useful for people interested in figuring out how the camera is working with various batteries.
To read this data successfully, you can use PhotoMe (I used 0.79R17 Build 856 works OK, v0.8beta2 build 891 doesn't display the data yet)
PhotoME - Exif, IPTC & ICC Metadata Editor
Open a K-x JPG and look under 'Manufacturers Notes'.
Below is what I see for the Energizer Lithium's supplied with the K-x when I bought it, after 998 RAW+ exposures. The Battery State is 3 out of 4. I'm not too sure what the other fields indicate.
Alternatively, using Phil Harvey's command-line ExifTool,
ExifTool by Phil Harvey
this is what you see based on the same image:
There's also lots of other useful info in there too, but the battery issue seems to be topical atm.
Just for info.