[ronnoch]

How would one go about setting this up in their own house? Privacy concerns aside, I can think a some cool uses for this (more finely-grained location based reminders for instance).

[biafra]

Doing the reverse might be easier. In Android you can see several access points and their strength. You can trilaterate or record fingerprints.

And it works anywhere where there is at least one or two visible wifis.

No special infrastructure needed.