The creator of Smart Alert for Mail obviously had a problem that no one else had been able to solve: Knowing when their mail had arrived. Enter Smart Alert for Mail--aka SAM--a gadget with a singular purpose, one which you've already figured out after reading this far. SAM comes in two pieces, a transmitter that fits in your mailbox and a receiver that sits inside your house. The transmitter attaches via sticky tape and Velcro to the inside of your mailbox (a small antenna wire snakes out through the gap in the door), while the receiver goes anywhere inside your house that's in range of a power outlet (and as close to the transmitter as possible). The transmitter communicates via the unlicensed 433.92MHz frequency band, which gives it 300 feet of range in unobstructed, open air.