Ocado, an online grocery store in England, prides itself on its delivery of refrigerated foods: When the company says the goods will arrive at a certain temperature, they mean it.

The promise is more than a marketing boast. Aided by microchip transmitters, heat sensors and a fast-growing form of wireless communication, the boast is a measurable fact.

Inside each Ocado delivery van is a SIM-card module the size of a postage stamp that monitors the air temperature. The sensor sends data to a computer used by fleet managers back at headquarters near London every few minutes.

Ocado says incidents of spoilage of goods have declined since the transmitters were installed last year.