Hundreds of children are killed every year in the US by accidental firearm discharges. Thousands of adults are injured every year from discharges too. Smart guns that restrict use to a single owner have failed so far because of political and engineering reasons. SmartMag ditches the idea of a modified gun and instead modifies the magazine. This allows retrofitting into the 300 million "un-smart" guns already out there, doesn't affect firearm reliability, and is easy to enable or disable. This addresses the main concerns of gun control opponents with smart guns, but still allows access restriction like gun control proponents have been advocating for.