The HHPL Checker notifies you through IFTTT when a book is available at Hamburg's public library.
First, set up an IFTTT webhook named hhpl and copy the key.
$ ./notify_book_availability.sh --ifttt_key=<key> T021736375The tool uses the public SOAP and JSON web service. I only discovered the existence of this API through paper, a tool to manage your library account.