Last thing which was missing was to add new router to monitoring using Munin which I use for this purpose. The only reasonable way seemed to be SNMP so I installed it to OpenWrt.
And the rest was incredibly simple! Just add snmp host to
munin.conf:
[openwrt.lan]
address localhost
And run SNMP discovery on monitoring host (the one which runs munin-node):
munin-node-configure-snmp openwrt.lan | sh
It automatically creates symlinks for everything it detects (network interfaces, load, disk space and users) and only remaining thing is to restart munin-node.
I'm starting to love this distribution. After few hours I've setup everything I needed including OpenVPN to other locations. Most of things were pretty easy to configure and basic settings can done as well over web interface.
The only thing I don't understand is that for some reason I don't see WAN IP address settiongs (I'm using static IP) and same way I lost WEP/WPA key configuration. Those parts of dialog simply do not appear on page while HTML is still there. I didn't yet have time to debug, but maybe later.