What was the first commercial application of microprocessors?

Busicom was a Japanese company that owned the rights to Intel's first microprocessor, the Intel 4004, which they created in partnership with Intel in 1970. Busicom asked Intel to design a set of integrated circuits for a new line of programmable electronic calculators in 1969. In doing this, they spurred the invention of Intel's first microprocessor to be commercialized, the Intel 4004. Busicom owned the exclusive rights to the design and its components in 1970 but shared them with Intel in 1971.