I wish this was more common, especially when traveling. When I have guests that need access to my wireless network I direct them to a QR code printed out and posted to a cabinet in the kitchen. Scanning this with most modern phones automatically connects it to my guest network.
Provide it a network SSID, security type (WPA) and password:
Usage: qr_code_wifi [OPTIONS] SSID SECURITY PASSWORD Options: --out FILENAME Save the QR code to the given path as a `png`. --help Show this message and exit.
Here's a link to the repository: