There are a few companies around providing geolocation APIs - Google, Navizon and Skyhook for example. What these companies do is to store information about location and visible networks (WiFi, cell sites) that allows them to calculate your location even if a GPS fix is not available (or even if a GPS is not available at all).
Navizon works on Windows Mobile devices, pretty much like Google Maps Mobile, with the added benefit that if you collect WiFi and cell site information then you can get paid for it (Google Maps does the same, but you don't see a dime).
Their software relies on a community of users who contribute this data to the system when they have a GPS-enabled Windows Mobile device.
Now comes the thing: Navizon actually pays for this data. All you need is to install it on your Windows Phone and have Navizon running in the background. Every WiFi access points that you pass, every cell site that you log will mean money in your pocket.
Here comes the shameless plug: if you plan on registering, please do so by clicking on the link below:
http://my.navizon.com/Webapps/UserAdmin/register.aspx?referral_code=595F5E and use my referral code (595F5E).
Obviously the opportunity here is that New Zealand hasn't been "mapped" yet - except for where I've been I presume...
I tried running another map software called Waze as suggested in other thread here, but the difference is that Waze is for a community of map builders, while Navizon is for a community of geolocation database builders. The map is already there, and their software just plots signals over the map.
This is the kind of database used behind Google Location API, that can be used on things like location sensors (check Geosense for Windows for an example of a location sensor).
Note the Navizon software works like Google Maps Mobile, but it's not as well polished. Their website does have some interesting features though, including alerts when friends come into an area you can create on a map. You can also have the software answer to SMS sent to your smartphone with its currenty location - very handy in case you lose it.