Couple Builds AI-Powered US Gas Price Tracker Using Vibe-Coding

Matt Cortland and John Fleming, a married couple based in London, launched a US gas price tracker called Gas Index on April 6, 2026. The project was developed using vibe-coding AI tools to speed up software development, creating a system that allows users to track fuel costs across the United States.

The application tracks more than 170,000 stations across all 50 states. It utilizes a combination of data sets, beginning with location and pricing data from Google. Because the founders noted that Google’s dataset covers only about half of US gas stations—with stronger coverage among large chains—Gas Index fills these gaps through user-submitted photos of pumps and receipts, as well as AI-generated phone calls.

Technical Development and Costs

The website was built using Claude Code over a period of three days. An additional two days were spent building the phone bot and managing data with the help of tools including Supabase, Twilio and ElevenLabs. The founders described the final 10% of the build process as very intensive.

The cost of AI token receipts for the project is estimated between $3,000 and $5,000. Cortland, a consultant, explained that costs increase with the volume of calls made, though the financial burden was mitigated by a grant of credits from ElevenLabs.

AI Interactions in the Field

A central component of the tracker is an AI agent named Bobby, named after a character from the sitcom King of the Hill. Bobby conducted nearly 20,000 conversations with gas station attendants to retrieve current pricing.

These interactions provided insight into how people react to AI in real-world settings. While most attendants answered the bot’s inquiries, some hesitated, and approximately one in every 700 calls involved profanity. The couple found that independently owned stations were the most willing to disclose their prices.

The data also revealed regional differences in communication. Texas was identified as the hardest state to reach by phone, and only 20% of stations in New Jersey shared pricing information after answering the call.

Consumer Context and Regional Comparisons

Gas Index attempts to translate rising fuel costs into everyday terms by comparing price spikes to regional delicacies. For example, a driver in Alewife, Massachusetts, can see how much more they are paying to fill their tank expressed in terms of fluffernutter ingredients or Dunkin’ iced coffees.

Other regional comparisons include:

• Nebraska: Gas prices are compared to the cost of a ticket for a Husker college football game.
• Louisiana: Costs are weighed against the price of a Cafe Du Monde beignet.
• New Hampshire: Prices are stacked against a pint of maple syrup.

Despite these features, accuracy varies due to the reliance on user-submitted data and the fact that gas prices can change multiple times per day. A spot-check by Business Insider of 10 stations found that four matched the listed price, while one differed by 15 cents.

Market Volatility and Regulatory Differences

John Fleming, a postdoctoral researcher at Oxford University, noted that the app highlights a significant difference in regulations between the US and the UK. In the UK, petrol stations are required to update prices every half hour and make that information publicly accessible, resulting in regional price differences of only three cents nationwide.

In the US, prices fluctuate more widely. On April 8, 2026, the national average for regular gas was $4.16 according to AAA, with prices ranging from $3.43 in Oklahoma to $5.93 in California.

The Gas Index website frames these increases around the war in Iran, stating on its homepage that gas is up $1.13 a gallon since the conflict began. While the site references the war, Cortland stated the goal is to help people in both Republican and Democratic states get better pricing.