Not quite 100% but neither is GasBuddy. Here are the two apps available for Android and iOS.
GasoApp (on Google Play)I haven´t tried it yet, but users say that the downside is updated information. Hey,it´s a start and I knew if GasBuddy didn´t do it, someone would.
Gasoapp is the official Energy Regulatory Commission (CRE) application of the that will allow you to locate the nearest gas station at the national level, lowest price or both, according to your location at that moment and type of fuel for a determined radius of kilometers . It has information about the products and prices of the gas stations allowed by the CRE, you can rate the service of the gas station and see the ratings that have been posted.
Guia Pemex is the other but it is only for Pemex labeled stations
Driving from the countryside yesterday to the northern most side of the Monterrey Metro area, prices ran the gamut. A lot depended on accessability on major thorough fares, level of residential areas and commercial centers nearby. I saw a price difference of 35 centavos, for our SUV that's about a 35 peso difference.