How do I know someone is tracking me over Wi-Fi?

In short, there is no way to determine when someone is tracking your location over Wi-Fi.

There are no settings that can be toggled on your mobile device (or any other access point), and there are no special apps that can help you determine if you are being tracked. The devices we use are not able to detect WPS tracking at all. However, you can use common sense to deduce whether you are being tracked at a given time.

For example, if you have allowed Google to track your location, WPS may be used to track you regardless of when this feature is enabled.

Also, if you activate Google services and you enter a multinational company's shop, there is a good chance that you will be tracked via Wi-Fi.

Other than that, your safest bet is to assume that you are always being tracked over Wi-Fi if you are near a router. Of course, this may not always be true; you're still more likely to be tracked over Wi-Fi when you're near a shop or a large organisation's router. However, if you want to stay safe, just assume that any router could be tracking your location.