I just came across this feature when I updated the Mobile Live Search client on my Windows Mobile phone. There now is a feature which allows you to find the lowest gas prices in your area. If you have a GPS enabled phone this feature is even easier to use. Currently the Mobile Live Search application is supported across a number of Windows Mobile versions in the US and UK and a beta version for Blackberry 4.0 and above in the US only. You can get the download here, http://www.microsoft.com/windowsmobile/livesearch/default.mspx

Happy motoring.