GasBag is a free iPhone application for finding the cheapest gas near you, with price data submitted by our users. It's been developed by 4 guys in Australia and the US. 

We think GasBag is unique in a few ways:
- Our map is, quite simply, the easiest-to-use gas price map on the iPhone
- Our users can send us price updates extremely quickly - just by tapping a station on the map, selecting a gas type, and scrolling the price dial
- We also include a logbook that calculates metrics like miles/gallon, average price/gallon, etc.
- Because the application knows where you are, how many gallons, and how much you paid to fill up, that also tells us the price at that station
- We have a twitter bot at @gbpr that takes address and pricing information from direct messages or replies
- Our users can add stations they spot directly, and we have over 100,000 stations in the database
- It's very simple to jump straight into the built-in Maps application if you want turn-by-turn directions

We've done a lot of work on the back-end servers and on the phone to make GasBag as easy to use as possible. We've kept it free to encourage the widest possible take-up, and our growth was so rapid it even caught us by surprise! We already have an advertising mechanism in place that provides unobtrusive, targeted ads, and we're looking to be cash-flow positive very shortly.

Since releasing it on the iTunes App Store a little over 4 weeks ago, we've rapidly built up a userbase of 75,000 unique users all over the United States. We have tens of thousands of users submitting price information through the direct and logbook methods, and the number grows daily, especially on the weekends. We're looking to expand to the United Kingdom, Australia, and Canada by the end of October, and then follow up on GasBag with other applications that use our same rich-mapping framework.

There's also a video of GasBag in action at http://blip.tv/file/1067165/.