For a while they had a paid program, I had a Windows Mobile app I could run with an external GPS dongle that would record wifi APs and location, upload to skyhook, who would occasionally cut me a check for my trouble. I made tens of dollars!
Interesting, wondering why Apple doesn't restrict the queries to its server using a certificate that would be pinned on the devices, etc, so at least you would need a legit iPhone/Mac to be able to do a query?
Permanent hardware or software IDs, such as the Windows GUID or machine-id on Linux (systemd) are inevitably abused for surveillance sooner or later.
For a while they had a paid program, I had a Windows Mobile app I could run with an external GPS dongle that would record wifi APs and location, upload to skyhook, who would occasionally cut me a check for my trouble. I made tens of dollars!