The Night Buyers, glad you asked, we're doing quite fine ;)
However, since we're at the beginning, there are periods (around 2:30-6:30am) when there are few orders. So, I said, let's help our drivers.
Which I did - I made a small program that monitors an email server. When a new email arrives (in our case, an order), a very loud sound is played continuously until the driver acknowledges the email.
Also, in case the internet connection is lost for more than 5 minutes (which in our case is critical), another sound will be played.
So far, the drivers are pretty happy with it - they can take a nap in those times, and if an order comes by, they're suddenly awake.
As libraries, I've used:
source code. I might add new features as my drivers ask them.