Gas Buddy is an iPhone App. that will show me the current gas prices for anywhere in the USA and Canada.  This means that if I am traveling down the road, I can check on the gas prices in the area and find the cheapest.

From my prospective, Gas Buddy tells me whether gas is cheaper in Lansing or Lowell or Grand Rapids.  So, when I am getting ready to head home and need to buy gas, it is nice to know whether I should buy it in Lansing or Lowell.