When looking to see who was running OpenBSD 3.3 on 486 boxes (more on this later), I discovered The Uptimes Project. Participants install a daemon on their systems which report uptimes to a central site. Beyond general statistics, you can check individual operating systems, such as FreeBSD. Maybe once my home network has been stabilized I will try this out. Maybe once I have stabilized my own network, I’ll try it out. I hope to see if it works in the future.”]
Source: https://taosecurity.blogspot.com/2003/08/os-uptime-project-when-looking-to-see.html