PeterH:
spinjector:
This would all be wired. There are half a dozen sites spread across 5 counties, about 35 miles at most, with microwave LAN bridges that use 802.11g over 900mhz diplexed onto the FCC licensed 950mhz band. But for the purpose of answering the question: it's "wired". =-)Also, at its max there would be a maximum of maybe like 18-20 remote Arduinos.
If you can provide access from each LAN to the public internet, and allow access from the public internet to a management station which can receive the incoming data, then the communication part becomes a simple TCP/IP design issue.
If you can't establish TCP/IP connectivity then the problem will be harder.
TCPIP is already established to the remote sites. Public internet is not needed, and is not an option for security reasons, that was the purpose of establishing private FCC-licensed IP links. The remote sites are subnetted as part of the LAN. Latency is usually less than 10ms. In fact it's fast enough that we use it for streaming audio and VOIP for phones at some sites, with nearly undetectable codec delay.