Possible to use ZIP code or city/state for location?

Would it be possible to add an option to use a ZIP code (or similar) to override the location provided by the iPhone? For whatever reason, the location service nearly always returns a location that is very, very wrong for me. Specifically, I'm on the western side of Houston, TX, and 90% of the time, the location service on the iPhone thinks I'm in Metarie, LA, 300 miles to the east.

The location service has never worked well for me. Originally, it got the right county (seriously: the "you-are-here" circle covered most of my county), but for about the past three weeks or so, it has decided I'm in a different state, and is very specific (but very wrong) about where it thinks I am.