Hey youxing !
we met in JFK airport if you remember!!
And, im not clear on the backup battery.

Are you talking about a SPARE battery that you use when one has run out of juice?
or are you talking about a battery INSIDE the phone itself for safety purposes etc?

If its the former, and your having problems with switching batteries constantly, battery hotswap IS possible. Its in the forum somewhere.

http://talk.maemo.org/showthread.php?t=57734

how you bin!?
hows the phone working out for you?