As Google Developer Expert I was involed in tester program of this API during alpha stage. My GDE's friend +Riël Notermans inspired me to connect Vision API into my favorite Google Apps Script. I was thinking how to use it and suddenly I found out useful something-like smart city solution.
Intro
I'm living in Prague. The municipal transportation provides almost real-time records of traffic from webcams The images are available on web (http://www.dpp.cz/en/webcams/). Anyone could check traffic before heading out to work. I am able to connect, download and send these images to any API, because each image has own public URL
The maps of webcams in Prague
I have created Google Spreadsheet as a database with new a Google Apps Script project.
Next step was activated required API in Google Developer Console. OAuth 2.0 dance was managed by great cGoa library by +Bruce Mcpherson. Cloud Vision "client" library was generated from Cloud Endpoints by +Spencer Easton's code.
My script fetched the image from URL as a Blob, converted into base64 and sent to Cloud Vision API with parameter for LABEL_DETECTION (Label detection tutorial available here)
As a JSON response I received description of image as labels with confidence score (min 0 - max 1).
The last step was setup Trigger for automatic run Apps Script every 5 minutes.
The result
I have run my script on webcam at Argentinska street at February 17th between 12am-12pm. The all collected data is available as interactive visualization. http://data.kutil.org/visualization/analysis-of-traffic-by-cloud-vision-apiThe label "road" means, that higher value looks like only street without street, so traffic during lunch was low.
It absolutely not 100% accurate, but it could inspire you how to use Google Cloud Vision API.