Navizon is a cool app for your mobile phone which works with a large database which users update to make it more accurate. The aim of the product is to allow those with out GPS receivers to find out where they are in cities. Those with a GPS device can track cellular towers and wifi signals as they drive around. Once the data is collected it is uploaded to a database. Those users with out GPS can then drive by and with triangulation work out where they are in a city due to signal strength on a cellular tower and wifi network names. The idea is quite cool and something I will be testing out in the next few weeks around my home town. Although the system would need a lot of data to track and also a number of wifi networks to make it accurate, you can see how this would be a very accurate system with in a busy city.
You can download Navizon here. The product costs $24.99 to buy which unfortunately is not much cheaper then a bluetooth receiver. Its well worth checking out the trial though.
