|I don't believe you'll find a way to send messages to other people's networks. Especially if they have a SOHO Router with a firewall up.|
I have seen Free wifi cafe's with a program or something that they call up to target a specific computer using their wifi, even though it is not set to their workgroup or domain
This was within one LAN. You're talking about sending to multiple separate LAN's which you're not a part of. This is a totally different situation and that messaging service likely won't work in your situation.
Can you not create a web page they can all connect to for info on the local internet. Maybe an email group including someone from each home......
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.