/usr/local/etc/nut/ups.conf

[Mustek]
    driver = megatec
    port = /dev/cuad1
    desc = "Mustek PowerMust 800 USB"

/usr/local/etc/nut/upsd.conf

ACL all 0.0.0.0/0
ACL localhost 127.0.0.1/32

ACCEPT localhost
REJECT all

/usr/local/etc/nut/upsd.users

[monuser]
    password = mustekpass))
    allowfrom = localhost
    upsmon master

/usr/local/etc/nut/upsmon.conf

MONITOR Mustek@localhost 1 monuser mustekpass)) master
MINSUPPLIES 1
SHUTDOWNCMD "/sbin/shutdown -r now"
NOTIFYCMD /usr/local/etc/nut/notify
POLLFREQ 5
POLLFREQALERT 5
HOSTSYNC 15
DEADTIME 15
POWERDOWNFLAG /etc/killpower
NOTIFYMSG ONBATT SYSLOG+WALL+EXEC
RBWARNTIME 43200
NOCOMMWARNTIME 300
FINALDELAY 5

/etc/rc.conf

nut_enable="YES"
nut_upslog_enable="YES"
nut_upsmon_enable="YES"

Пишем в /usr/local/etc/nut/notify что-то вроде

#!/bin/sh
echo 'Power Down on host http://siegerstein.net' | mail -s'Mustek PowerMust 800 USB' siegerstein@localhost

chmod +x /usr/local/etc/nut/notify

Перезапуск компа. UPS подключен к COM2 (cuad1)