Door hangers.
A technician leaves a hanger at homes around the job. The neighbor may not be home — the hanger still puts your name on the street where you just did good work.
Verifiable Action: To get credit, the technician takes a photo of the door hanger on the doorstep. The photo is time-stamped and geo-tagged, and in the owner portal you can see a map of the activities before you approve the reward.