I'm not sure what the solution is, but my worry with tying to an IP address is the mobile setting where I may transition from work wifi to bus wifi to home wifi

I'm not sure what the solution is, but my worry with tying to an IP address is the mobile setting where I may transition from work wifi to bus wifi to home wifi, with a mobile carrier in between all of those steps. Maybe something like a device ID, although I assume that that can be easily stolen and spoofed.