The move comes as the tech specialist looks to develop its international operations.
Kaday's role is part-time. Last weekend, he led a workshop on new-business development at a meeting for staff from across the agency's European network.
Kaday joined B-M in 1986, managing tech accounts and working on new business, but left two years later to found Hi-Tech Marketing, which he sold in 2000 to direct-marketing specialist Harte-Hanks.
He has since been writing, speaking in public and doing consultancy work.