To install the acpi daemon and modules:

# tazpkg get-install acpid
# tazpkg get-install linux-acpi

The acpi daemon needs to be started before dbus and hal, so edit your /etc/rcS.conf to look like this:

RUN_DAEMONS="acpid, dbus, hald, etc..."

Or, to start manually:

# /etc/init.d/hald stop
# /etc/init.d/dbus stop
# /etc/init.d/acpid start
# /etc/init.d/dbus start
# /etc/init.d/hald start

To check it's working, just:

$ cat /proc/acpi/battery/{BAT0}/info

You can find some example scripts in /etc/acpi.