Making "call and response" literal - rotary phone, you could call and it would immediately dial a number, a prompt telling you to say something. pay as you go cellphone to a staff member/transcriber/listener/operator.

A random phone on campus, video camera pointed at it

Panoptos walkie talkies, hanging on the wall, call for help

Telephone by the joystick station that would ring and the person in the salon, try to get the person to get to a certain place to take a photo - kind of like playing telephone with object hunt

A path/scavenger hunt, narrative.

Having people start off at a certain point, then prompts to create your own paths.

Find a painting that makes you feel X

Choose your own adventure