This probably is old news, but on the spare dsm (isfs8) with just barometer and gps inputs, the power consumption is:
12.5V @ 0.55A = 6.9W (router on with ssh connection, but no udp data)
12.5V @ 0.31A = 3.9W (router turned off by: viper_dio /dev/viper_dio0 7 0)
for a difference of 3.0W.