You can configure a bitcoin core node to observe new transactions and notify you about them.
This is a preferable solution, since you will not have to trust anyone to provide you with the correct information (what if they lie or are incorrect?), And you will retain your privacy (why bother with the addresses that you are interested in, to the API provider and to anyone else who listens to your connection?).
You can configure the command
-walletnotify= in your bitcoin.conf file and write a bash script to alert you of the transaction in question, however you prefer (write to a log file, send an email alert, a light flashes, etc.).
For a slightly deeper tutorial on how to configure this, see this question: How do I use walletnotify?