If someone is intrested here is second (undebugged) incarnation of my hostnames updater script:

#!/bin/sh
#verze 2.0.0_2013-05-31
lock=/var/run/hostnames-updater.pid
shmm="/dev/shm/hosts"

clean () {
    rm $lock
    rm $shmm
}
trap clean SIGHUP SIGINT SIGTERM

/bin/echo $$ > $lock
while /bin/true
    tst(){
    x=0
    if $3 = $(/usr/bin/ssh-keyscan -p $2 $5 2>/dev/null|/bin/sed 's/.*\ ssh-.*\ //g'|/usr/bin/whirpooldeep)
    then
        x=$5
    elif /usr/bin/test $1 -gt 2
    then
        if $3 = $(/usr/bin/ssh-keyscan -p $2 $6 2>/dev/null|/bin/sed 's/.*\ ssh-.*\ //g'|/usr/bin/whirlpooldeep)
        then
            x=$6
        else
            x=$4
        fi
    else
        x=$4
    fi
    }

#host testing line is as folows
#tst <number of addresses to try - some hosts do have wl and eth interface)> \
#<output of  ssh-keyscan -p <port> <address> 2>/dev/null|/bin/sed 's/.*\ ssh-.*\ //g'|/usr/bin/whirlpooldeep> \
#<fallback address - eg. vpn one> <address 2> <address n>

####################host 1
tst <address count n> <port> <hash> <address 1 > ... <address n> 2>&1 >/dev/null
host1=$x


#lets create hosts file
/bin/echo "# /etc/hosts: Local Host Database
#
# This file describes a number of aliases-to-address mappings for the for
# local hosts that share this file.
#
# In the presence of the domain name service or NIS, this file may not be
# consulted at all; see /etc/host.conf for the resolution order.
#

# IPv4 and IPv6 localhost aliases
127.0.0.1    $(hostname).local $(hostname) localhost
::1        localhost

#
# Imaginary network.
    $host1        host1
#    Last update $(date --rfc-3339)

#
#
# According to RFC 1918, you can use the following IP networks for private
# nets which will never be connected to the Internet:
#
#       10.0.0.0        -   10.255.255.255
#       172.16.0.0      -   172.31.255.255
#       192.168.0.0     -   192.168.255.255
#
# In case you want to be able to connect directly to the Internet (i.e. not
# behind a NAT, ADSL router, etc...), you need real official assigned
# numbers.  Do not try to invent your own network numbers but instead get one
# from your network provider (if any) or from your regional registry (ARIN,
# APNIC, LACNIC, RIPE NCC, or AfriNIC.)
#
" > $shmm
/bin/mv $shmm /etc/hosts
/usr/bin/sleep 300
done


I hope I helps someone
S