Show list of clients of wifi hotspot Mac OS X
I get the list using arp command at Terminal.

first, get your WiFi sharing interface name, I get it by typing ifconfig on terminal.

It should be something like bridgexxx, for me, it's bridge100

Then type this on terminal:

arp -i interfacename -a

for me the command was like:

arp -i bridge100 -a

it shows the internal ip addresses and mac addresses of the devices connected.