Hi Dave, this is a nice question and the answer is YES.
The PCB’s have been designed with a connector where you can add a clicker. See it in the picture attached.
I recommend the self oscillating 3V piezo buzzers. Here’s an examples:
http://www.ebay.com/itm/Black-3V-Electromagnetic-Type-Piezo-Buzzer-Continuous-Sound-Pack-of-20-/271455683312?hash=item3f340502f0:g:b9wAAOSwu4BVyxYp
You will also need a firmware upgrade, as by default the digital output pulses on that connector are disabled.
Radu
