Interface sensor fails

Binary package hint: watchdog

syslog:Jun 10 11:57:37 black watchdog[9686]: starting daemon (5.9):
syslog:Jun 10 11:57:37 black watchdog[9686]: int=1s realtime=yes sync=no soft=no mla=24 mem=0
syslog:Jun 10 11:57:37 black watchdog[9686]: ping: no machine to check
syslog:Jun 10 11:57:37 black watchdog[9686]: file: /var/log/syslog:1407
syslog:Jun 10 11:57:37 black watchdog[9686]: pidfile: /var/run/rsyslogd.pid
syslog:Jun 10 11:57:37 black watchdog[9686]: interface: eth0
syslog:Jun 10 11:57:37 black watchdog[9686]: interface: br0
syslog:Jun 10 11:57:37 black watchdog[9686]: test=none(0) repair=none(0) alive=none heartbeat=none temp=none to=root no_act=no
syslog:Jun 10 11:57:37 black kernel: [75280.713899] watchdog (9686): /proc/9686/oom_adj is deprecated, please use /proc/9686/oom_score_adj instead.
syslog:Jun 10 11:57:38 black watchdog[9686]: device eth0 did not receive anything since last check
syslog:Jun 10 11:57:38 black watchdog[9686]: shutting down the system because of error 101

This is nonsense, as eth0 is up, and watchdog is shutting down the system just 1 second after being started, claiming it's not.

Also, watchdog can't ping properly, from a prior try pinging to an address nearby, confirmed by pinging in a console to be available:
syslog.1:Jun 9 15:02:26 black watchdog[2497]: no response from ping (target: [IP address here])
syslog.1:Jun 9 15:02:26 black kernel: [ 133.646779] watchdog (2497): /proc/2497/oom_adj is deprecated, please use /proc/2497/oom_score_adj instead.
syslog.1:Jun 9 15:02:26 black watchdog[2497]: shutting down the system because of error 101

The is Ubuntu 11.04. There's a smaller problem in your sample config file, in that you have it suggesting monitoring /var/log/messages, which isn't used in 11.04.