AUSTIN, Tex. — Which product at this year’s South by Southwest technology conference received more attention than perhaps any other?

Homeless people as wireless transmitters.

A marketing agency touched off a wave of criticism and debate when it hired members of the local homeless population to walk around carrying mobile Wi-Fi devices, offering conferencegoers Internet access in exchange for donations.

BBH Labs, the innovation unit of the international marketing agency BBH, outfitted 13 volunteers from a homeless shelter with the devices, business cards and T-shirts bearing their names: “I’m Clarence, a 4G Hotspot.” They were told to go to the most densely packed areas of the conference, which has become a magnet for those who want to chase the latest in technology trends.